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Contra Costa County (; ''Contra Costa'',
Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many countries in the Americas **Spanish cuisine **Spanish history **Spanish culture ...
for 'Opposite Coast') is a
county A county () is a geographic region of a country used for administrative or other purposesL. Brookes (ed.) '' Chambers Dictionary''. Edinburgh: Chambers Harrap Publishers Ltd, 2005. in some nations. The term is derived from the Old French denoti ...
located in the U.S. state of
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
, in the
East Bay The East Bay is the eastern region of the San Francisco Bay Area and includes cities along the eastern shores of San Francisco Bay and San Pablo Bay. The region has grown to include inland communities in Alameda and Contra Costa counties. Wi ...
of the
San Francisco Bay Area The San Francisco Bay Area, commonly known as the Bay Area, is a List of regions of California, region of California surrounding and including San Francisco Bay, and anchored by the cities of Oakland, San Francisco, and San Jose, California, S ...
. As of the 2020 United States census, the population was 1,165,927. The
county seat A county seat is an administrative center, seat of government, or capital city of a county or parish (administrative division), civil parish. The term is in use in five countries: Canada, China, Hungary, Romania, and the United States. An equiva ...
is Martinez. It occupies the northern portion of the
East Bay The East Bay is the eastern region of the San Francisco Bay Area and includes cities along the eastern shores of San Francisco Bay and San Pablo Bay. The region has grown to include inland communities in Alameda and Contra Costa counties. Wi ...
region of the
San Francisco Bay Area The San Francisco Bay Area, commonly known as the Bay Area, is a List of regions of California, region of California surrounding and including San Francisco Bay, and anchored by the cities of Oakland, San Francisco, and San Jose, California, S ...
and is primarily
suburb A suburb (more broadly suburban area) is an area within a metropolitan area. They are oftentimes where most of a metropolitan areas jobs are located with some being predominantly residential. They can either be denser or less densely populated ...
an. The county's name refers to its position on the other side of the bay from
San Francisco San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...
. Contra Costa County is included in the
San Francisco–Oakland–Berkeley, CA Metropolitan Statistical Area The San Francisco Bay Area, commonly known as the Bay Area, is a region of California surrounding and including San Francisco Bay, and anchored by the cities of Oakland, San Francisco, and San Jose. The Association of Bay Area Governments de ...
.


History


Pre-human

In prehistoric times, particularly the
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...
, portions of the landforms now in the area (then marshy and grassy
savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) biome and ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach th ...
) were populated by a wide range of now extinct
mammals A mammal () is a vertebrate animal of the class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle e ...
, known in modern times by the
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
remains excavated in the southern part of the county. In the northern part of the county, significant coal and sand deposits were formed in even earlier geologic eras. Other areas of the county have ridges exposing ancient but intact (not fossilized) seashells, embedded in
sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...
layers alternating with
limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
. Layers of volcanic ash ejected from geologically recent but now extinct
volcanoes A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often fo ...
, compacted and now tilted by compressive forces, may be seen at the site of some road excavations. This county is an agglomeration of several distinct geologic
terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its d ...
s, as is most of the greater
San Francisco Bay Area The San Francisco Bay Area, commonly known as the Bay Area, is a List of regions of California, region of California surrounding and including San Francisco Bay, and anchored by the cities of Oakland, San Francisco, and San Jose, California, S ...
, which is one of the most geologically complex regions in the world. The great local mountain
Mount Diablo Mount Diablo is a mountain of the Diablo Range, in Contra Costa County, California, Contra Costa County of the eastern San Francisco Bay Area in Northern California. It is south of Clayton, California, Clayton and northeast of Danville, Califo ...
has been formed and continues to be elevated by compressive forces resulting from the action of
plate tectonics Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...
and at its upper reaches presents ancient seabed rocks scraped from distant oceanic sedimentation locations and accumulated and lifted by these great forces. Younger deposits at middle altitudes include
pillow lava Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava underwater, or ''subaqueous extrusion''. Pillow lavas in volcanic rock are characterized by thick sequences of discontinu ...
s, the product of undersea volcanic eruptions.


Native American period

The
Bay Miwok The Bay Miwok are a cultural and linguistic group of Miwok, a Native Americans in the United States, Native American people in Northern California who live in Contra Costa County, California, Contra Costa County. They joined the Franciscan missi ...
,
Yokut The Yokuts (previously known as MariposasPowell, 1891:90–91.) are an ethnic group of Native Americans native to central California. Before European contact, the Yokuts consisted of up to 60 tribes speaking several related languages. Yokuts ...
and
Ohlone The Ohlone ( ), formerly known as Costanoans (from Spanish meaning 'coast dweller'), are a Native Americans in the United States, Native American people of the Northern California coast. When Spanish explorers and missionaries arrived in the l ...
people lived in the area now known as Contra Costa County before the arrival of Spanish colonists. The Volvon triblet of the Miwok lived on Tuyshtak (
Mount Diablo Mount Diablo is a mountain of the Diablo Range, in Contra Costa County, California, Contra Costa County of the eastern San Francisco Bay Area in Northern California. It is south of Clayton, California, Clayton and northeast of Danville, Califo ...
near present day Walnut Creek) until they were forcibly moved from their land into the Spanish missions in the early 1800s. The
Saklan tribe The Saklan are a tribe of the Native American Miwok community, based just south of San Pablo and Suisun Bays, in Contra Costa County, California. Their historical tribal lands ranged from Moraga, to San Leandro Creek, to Lafayette. History ...
lived between Moraga, along
San Leandro Creek San Leandro Creek () is a year-round natural stream in the hills above Oakland in Alameda County and Contra Costa County of the East Bay in northern California.U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe ...
, to Lafayette. Beginning in 1772, expeditions of Spanish missionaries and soldiers from
Mission San José Mission San José may refer to: *Mission San José (California), a Spanish mission in Fremont, California *Mission San Jose, Fremont, California, a neighborhood *Mission San Jose High School, a high school in Fremont, California *Mission San José ( ...
entered the
San Ramon Valley The San Ramon Valley is a valley and region in Contra Costa County and Alameda County, in the East Bay region of the San Francisco Bay Area in northern California. Geography The valley is between the Oakland Hills on the west, and the Diablo R ...
. Early contact was fleeting and mostly peaceful, however, in the late 1700s, Spanish cattle were grazed the territory of the Saklan and their neighbors. The Saklans were one of the few groups who mounted resistance against the efforts of the Spanish to convert them to Christianity. Christian natives were sent to the Saklans to convince them to give up their culture and come to Mission San Jose; they were killed by the Saklans who wanted nothing to do with the Spanish way of life. A punitive expedition was sent to the area in 1797 to repress the Saklans, and a battle was fought in modern-day Lafayette. In the early 1800s, many Saklan fled to the mission as a result of societal collapse from disease. By the 1810s the Saklan's tribal range was essentially devoid of inhabitants.


Spanish colonial

Early interaction of these Native Americans with Europeans came with the Spanish colonization via the establishment of missions in this area, with the missions in San Jose, Sonoma, and San Francisco and particularly the establishment of a
Presidio A presidio (''jail, fortification'') was a fortified base established by the Spanish Empire mainly between the 16th and 18th centuries in areas under their control or influence. The term is derived from the Latin word ''praesidium'' meaning ''pr ...
(a military establishment) in 1776. Although there were no missions established within this county, Spanish influence here was direct and extensive, through the establishment of land grants from the King of Spain to favored settlers.


Mexican land grants

In 1821 Mexico gained independence from Spain. While little changed in ranchero life, the
Mexican War of Independence The Mexican War of Independence (, 16 September 1810 – 27 September 1821) was an armed conflict and political process resulting in Mexico's independence from the Spanish Empire. It was not a single, coherent event, but local and regional ...
resulted in the secularization of the missions with the re-distribution of their lands, and a new system of land grants under the Mexican Federal Law of 1824. Mission lands extended throughout the Bay Area, including portions of Contra Costa County. Between 1836 and 1846, during the era when California was a province of independent Mexico, the following 15 land grants were made in Contra Costa County. The smallest unit was one square league, or about seven square miles, or , maximum to one individual was eleven leagues, or , including no more than of irrigable land. Rough surveying was based on a map, or ''diseño'', measured by streams, shorelines, and/or horseman who marked it with rope and stakes. Lands outside rancho grants were designated ''el sobrante'', as in surplus or excess, and considered common lands. The law required the construction of a house within a year. Fences were not required and were forbidden where they might interfere with roads or trails. Locally a large family required roughly 2000 head of cattle and two square leagues of land (fourteen square miles) to live comfortably. Foreign entrepreneurs came to the area to provide goods that Mexico could not, and trading ships were taxed.For a collection of observations of the Mexican provincial culture and trading practice (most notably in the acquisition of cattle hides for eastern U.S. shoe manufacturies) see portions of ''
Two Years Before the Mast ''Two Years Before the Mast'' is a memoir by the American author Richard Henry Dana Jr., published in 1840, having been written after a two-year sea voyage from Boston to California on a merchant ship starting in 1834. A Two Years Before the Mast ...
'', a first-person narrative of a seaman's voyage to California starting in 1834.
*
Rancho Cañada de los Vaqueros Rancho or Ranchos may refer to: Settlements and communities *Rancho, Aruba, former fishing village and neighbourhood of Oranjestad *Ranchos of California, 19th century land grants in Alta California ** List of California Ranchos * Ranchos, Buenos ...
was granted to Francisco Alviso, Antonio Higuera, and Manuel Miranda ( confirmed in 1889 to heirs of Robert Livermore). * Two ranchos, both called Rancho San Ramon, were granted by the Mexican government in the San Ramon Valley. In 1833, Bartolomé Pacheco (southern San Ramon Valley) and Mariano Castro (northern San Ramon Valley) shared the two square league Rancho San Ramon. José María Amador was granted a four square league Rancho San Ramon in 1834. * In 1834
Rancho Monte del Diablo Rancho Monte del Diablo (Devil's Mount Ranch in Spanish) was a Mexican land grant in present-day Contra Costa County, California given in 1834 by Governor José Figueroa to Salvio Pacheco. The name "Monte del Diablo" means "thicket of the devil" ...
(present day
Concord, California Concord ( ) is the most populous city in Contra Costa County, California, Contra Costa County, California, United States. According to an estimate completed by the United States Census Bureau, the city had a population of 124,016 in 2024, maki ...
) was confirmed with to Salvio Pacheco (born July 15, 1793, died 1876). The Pacheco family settled at the Rancho in 1846 (between the Pacheco shipping port townsite and Clayton area, and including much of Lime Ridge). The boundary lines were designated with stone markers. Clayton was later located on El Sobrante's lands just east of Rancho Monte del Diablo (
Mount Diablo Mount Diablo is a mountain of the Diablo Range, in Contra Costa County, California, Contra Costa County of the eastern San Francisco Bay Area in Northern California. It is south of Clayton, California, Clayton and northeast of Danville, Califo ...
). * In 1834,
Rancho Arroyo de Las Nueces y Bolbones Rancho Arroyo de Las Nueces y Bolbones (also called "San Miguel") was a Mexican land grant in present-day Contra Costa County, California given in 1834 by Governor José Figueroa to Juana Sanchez de Pacheco. The grant was named after the pr ...
, aka
Rancho San Miguel Rancho San Miguel is a neighborhood in Walnut Creek, California. It is named after the Alta California Rancho Rancho Arroyo de Las Nueces y Bolbones which was also referred to as Rancho San Miguel. Until the mid-1950s the area consisted largely of ...
(present day Walnut Creek), was granted to Juana Sanchez de Pacheco, in recognition of the service of Corporal Miguel Pacheco 37 years earlier (confirmed 1853, patented to heirs 1866); the grant was for two leagues, but drawn free hand on the ''diseño''/map, and reading "two leagues, more or less" as indicated in the ''diseño'', but actually including and confirmed for nearly four leagues or nearly , but only were ever shown as having once belonged to Juana Sanchez. * 'Meganos' means 'sand dunes.' A "paraje que llaman los Méganos" 'place called the sand dunes' (with a variant spelling) is mentioned in Durán's diary on May 24, 1817. Two Los Meganos Ranchos were granted, later differentiated as
Rancho Los Meganos Rancho or Ranchos may refer to: Settlements and communities *Rancho, Aruba, former fishing village and neighbourhood of Oranjestad *Ranchos of California, 19th century land grants in Alta California ** List of California Ranchos * Ranchos, Buenos ...
(1835, three leagues or at least ) in what is now the Brentwood area, to Jose Noriega then acquired by
John Marsh John Marsh may refer to: Politicians * John Marsh (MP fl. 1394–1397), MP for Bath *John Marsh (MP fl. 1414–1421), MP for Bath *John Allmond Marsh (1894–1952), Canadian Member of Parliament * John Otho Marsh Jr. (1926–2019), American co ...
; and
Rancho Los Medanos Rancho Los Medanos (from the Spanish: ''Rancho Los Médanos'' meaning Sand Dunes Ranch) was a Mexican land grant in present-day Contra Costa County, California given in 1839 by Governor Juan Alvarado to Jose Antonio Mesa and Jose Miguel Garcia. ...
(to Jose Antonio Mesa and Jose Miguel Garcia, Pittsburg area, dated November 26, 1839).


Bear Flag Republic and statehood

The exclusive land ownership in California by
Hispanic The term Hispanic () are people, Spanish culture, cultures, or countries related to Spain, the Spanish language, or broadly. In some contexts, Hispanic and Latino Americans, especially within the United States, "Hispanic" is used as an Ethnici ...
s in California would soon end.
John Marsh John Marsh may refer to: Politicians * John Marsh (MP fl. 1394–1397), MP for Bath *John Marsh (MP fl. 1414–1421), MP for Bath *John Allmond Marsh (1894–1952), Canadian Member of Parliament * John Otho Marsh Jr. (1926–2019), American co ...
, owner of
Rancho Los Meganos Rancho or Ranchos may refer to: Settlements and communities *Rancho, Aruba, former fishing village and neighbourhood of Oranjestad *Ranchos of California, 19th century land grants in Alta California ** List of California Ranchos * Ranchos, Buenos ...
in Contra Costa County, sent letters to influential people in the eastern United States extolling the climate, soil, and potential for agriculture in California, with the purpose of encouraging Americans to immigrate to California and lead to its becoming part of the United States. His letters were published in newspapers throughout the East which started the first wagon trains to California. He invited the settlers to stay on his ranch , and Rancho Los Meganos became the terminus of the California trail. This led to the
Bear Flag Revolt The California Republic, or Bear Flag Republic, was an List of historical unrecognized states#Americas, unrecognized breakaway state from Second Federal Republic of Mexico, Mexico, that existed from June 14, 1846 to July 9, 1846. It milita ...
in 1846 when about 30 settlers originally from the United States declared a
republic A republic, based on the Latin phrase ''res publica'' ('public affair' or 'people's affair'), is a State (polity), state in which Power (social and political), political power rests with the public (people), typically through their Representat ...
in June 1846 and were enlisted and fighting under the U.S. flag by July 1846. Following the
Mexican–American War The Mexican–American War (Spanish language, Spanish: ''guerra de Estados Unidos-México, guerra mexicano-estadounidense''), also known in the United States as the Mexican War, and in Mexico as the United States intervention in Mexico, ...
of 1846–48, California was controlled by U.S. settlers organized under the
California Battalion The California Battalion (also called the first California Volunteer Militia and U.S. Mounted Rifles) was formed during the Mexican–American War (1846–1848) in present-day California, United States. It was led by U.S. Army Brevet (military) ...
and the
U.S. Navy The United States Navy (USN) is the maritime service branch of the United States Department of Defense. It is the world's most powerful navy with the largest displacement, at 4.5 million tons in 2021. It has the world's largest aircraft ...
's
Pacific Squadron The Pacific Squadron of the United States Navy, established c. 1821 and disbanded in 1907, was a naval squadron stationed in the Pacific Ocean in the 19th and early 20th centuries. Developing from a small force protecting United States commerc ...
. After some minor skirmishes, California was under U.S. control by January 1847 and formally annexed and paid for by the U.S. in 1848. By 1850, California's population of over 100,000 was rapidly growing due to the
gold rush A gold rush or gold fever is a discovery of gold—sometimes accompanied by other precious metals and rare-earth minerals—that brings an onrush of miners seeking their fortune. Major gold rushes took place in the 19th century in Australia, ...
and the large amount of gold being exported east, which gave California enough clout to choose its own boundaries, write its own constitution, and be admitted to the Union as a free state in 1850 without going through territorial status as required for most other states. In 1850 California had a non-Indian population of over 100,000. The number of Indians living in California in 1850 has been estimated to be from 60,000 to 100,000. By 1850 the Mission Indian populations had largely succumbed to disease and abuse and only numbered a few thousand. California's 1852 state Census gives 31,266 Indian residents, but this is an under-count since there was little incentive and much difficulty in getting it more correct.


County creation

Contra Costa County was one of the original 27 counties of California, created in 1850 at the time of statehood. The county was originally to be called Mt. Diablo County, but the name was changed prior to incorporation as a county. The county's
Spanish language Spanish () or Castilian () is a Romance languages, Romance language of the Indo-European languages, Indo-European language family that evolved from the Vulgar Latin spoken on the Iberian Peninsula of Europe. Today, it is a world language, gl ...
name means ''opposite coast'', because of its location opposite San Francisco, in an easterly direction, on
San Francisco Bay San Francisco Bay (Chochenyo language, Chochenyo: 'ommu) is a large tidal estuary in the United States, U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the cities of San Francisco, California, San ...
. Southern portions of the county's territory, including all of the bayside portions opposite San Francisco and northern portions of
Santa Clara County Santa Clara County, officially the County of Santa Clara, is the sixth-most populous county in the U.S. state of California, with a population of 1,936,259 as of the 2020 census. Santa Clara County and neighboring San Benito County form the ...
, were given up to form
Alameda County Alameda County ( ) is a county located in the U.S. state of California. As of the 2020 census, the population was 1,682,353, making it the 7th-most populous county in the state and 21st most populous nationally. The county seat is Oakland. A ...
effective March 25, 1853. The land titles in Contra Costa County may be traced to multiple subdivisions of a few original land grants. The grantee's family names live on in a few city and town names such as '' Martinez'', '' Pacheco'' and '' Moraga'' and in the names of streets, residential subdivisions, and business parks. A few mansions from the more prosperous farms have been preserved as museums and cultural centers and one of the more rustic examples has been preserved as a working demonstration ranch
Borges Ranch
In the 1860 United States Census, Contra Costa County had a population of 4,381.


1941–1945

During World War II,
Richmond Richmond most often refers to: * Richmond, British Columbia, a city in Canada * Richmond, California, a city in the United States * Richmond, London, a town in the London Borough of Richmond upon Thames, England * Richmond, North Yorkshire, a town ...
hosted one of the two Bay Area sites of
Kaiser Shipyards The Kaiser Shipyards were seven major shipbuilding yards located on the West Coast of the United States, United States west coast during World War II. Kaiser ranked 20th among U.S. corporations in the value of wartime production contracts. The ...
and wartime pilots were trained at what is now Concord/Buchanan Field Airport. Additionally, a large Naval Weapons Depot and munitions ship loading facilities at Port Chicago remain active to this day, but with the inland storage facilities recently declared surplus, extensive redevelopment is being planned for this last large central-county tract. The loading docks were the site of a devastating explosion in 1944. Port Chicago was bought out and demolished by the Federal Government to form a safety zone near the Naval Weapons Station loading docks. At one time the Atlas Powder Company (subsequently closed) produced gunpowder and dynamite. The site of the former Atlas Powder Company is located at
Point Pinole Regional Shoreline Point Pinole Regional Shoreline is a regional park on the shores of the San Pablo Bay, California (the northern arm of the San Francisco Bay), in the United States. It is approximately in area, and is operated by the East Bay Regional Park Dis ...
, part of the
East Bay Regional Parks District The East Bay Regional Park District (EBRPD) is a special district operating in Alameda County and Contra Costa County, California, within the East Bay area of the San Francisco Bay Area. It maintains and operates a system of regional parks which ...
.


1945-present day

With the postwar
baby boom A baby boom is a period marked by a significant increase of births. This demography, demographic phenomenon is usually an ascribed characteristic within the population of a specific nationality, nation or culture. Baby booms are caused by various ...
and the desire for suburban living, large
tract housing Tract housing, sometimes informally known as cookie cutter housing, is a type of housing development in which multiple similar houses are built on a tract (area) of land that is subdivided into smaller lots. Tract housing developments are found ...
developers would purchase large central county farmsteads and develop them with roads, utilities and housing. Once mostly rural walnut orchards and cattle ranches, the area was first developed as low-cost, large-lot suburbs, with a typical low-cost home being placed on a "quarter-acre" (1,000 m2) lot — actually a little less at . Some of the expansion of these suburban areas was clearly attributable to
white flight The white flight, also known as white exodus, is the sudden or gradual large-scale migration of white people from areas becoming more racially or ethnoculturally diverse. Starting in the 1950s and 1960s, the terms became popular in the Racism ...
from decaying areas of
Alameda County Alameda County ( ) is a county located in the U.S. state of California. As of the 2020 census, the population was 1,682,353, making it the 7th-most populous county in the state and 21st most populous nationally. The county seat is Oakland. A ...
and the
consolidated city-county In local government in the United States, United States local government, a consolidated city-county (#Terminology, see below for alternative terms) is formed when one or more city, cities and their surrounding County (United States), county (Lis ...
of
San Francisco San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...
, but much was due to the postwar
baby boom A baby boom is a period marked by a significant increase of births. This demography, demographic phenomenon is usually an ascribed characteristic within the population of a specific nationality, nation or culture. Baby booms are caused by various ...
of the era creating demand for three- and four-bedroom houses with large yards that were unaffordable or unavailable in the established bayside cities. A number of large companies followed their employees to the suburbs, filling large business parks. The establishment of a large, prosperous population in turn fostered the development of large shopping centers and created demand for an extensive supporting infrastructure including roads, schools, libraries, police, firefighting, water, sewage, and flood control. The establishment of the
Bay Area Rapid Transit Bay Area Rapid Transit (BART) is a rapid transit system serving the San Francisco Bay Area in California. BART serves 50 stations along six routes and of track, including eBART, a spur line running to Antioch, and Oakland Airport Connecto ...
(BART) system, the modernization of Highway 24, and the addition of a fourth
Caldecott Tunnel The Caldecott Tunnel is a four-bore highway tunnel through the Berkeley Hills between Oakland and Orinda, California. Its four bores carry California State Route 24. Named after Thomas E. Caldecott, former mayor of Berkeley, it opened in ...
bore all served to reinforce the demographic and economic trends in the
Diablo Valley The Diablo Valley refers to a valley in the East Bay of the San Francisco Bay Area, to the west/northwest of Mount Diablo. The valley contains the cities of Clayton, Concord, Martinez, Pleasant Hill (home to Diablo Valley College), most of W ...
area, with cities such as Walnut Creek and
Concord Concord may refer to: Meaning "agreement" * Harmony, in music * Agreement (linguistics), a change in the form of a word depending on grammatical features of other words Arts and media * ''Concord'' (video game), a defunct 2024 first-person sh ...
becoming
edge cities An edge city is a concentration of business, shopping, and entertainment outside a traditional downtown or central business district, in what had previously been a suburban, residential or rural area. The term was popularized by the 1991 boo ...
. The central county cities have in turn spawned their own suburbs within the county, extending east along the county's estuarine north shore; with the older development areas of
Bay Point Bay Point may refer to: * Bay Point (Antarctica) * Bay Point, California * Bay Point (former settlement), California * Bay Point, Monroe County, Florida * Bay Point (South Carolina), in Charleston, South Carolina's harbor; see Mitchelville * B ...
and
Pittsburg Pittsburg may refer to: Places United States Cities, towns, townships and counties *Pittsburg, California * Pittsburg, Florida *Pittsburg, Kansas, Crawford County *Pittsburg, New Hampshire * Pittsburg, Oklahoma *Pittsburg, Texas *Pittsburg Coun ...
being augmented by extensive development in
Antioch Antioch on the Orontes (; , ) "Antioch on Daphne"; or "Antioch the Great"; ; ; ; ; ; ; . was a Hellenistic Greek city founded by Seleucus I Nicator in 300 BC. One of the most important Greek cities of the Hellenistic period, it served as ...
, Oakley, and Brentwood. The effects of the housing value crash (2008–2011) varied widely throughout the county. Values of houses in prosperous areas with good schools declined only modestly in value, while houses recently built in outlying suburbs in the eastern part of the county experienced severe reductions in value, accelerated by high unemployment and consequent mortgage foreclosures, owner ''strategic walk-aways'', and the too-rapid conversion of neighborhoods from owner-occupancy to rentals. Home values rebounded as the economy recovered from the recession.


Geography

According to the
U.S. Census Bureau The United States Census Bureau, officially the Bureau of the Census, is a principal agency of the U.S. federal statistical system, responsible for producing data about the American people and economy. The U.S. Census Bureau is part of the U ...
, the county has a total area of , of which is land and (11%) is water. Contra Costa County's physical geography is dominated by the bayside alluvial plain, the
Oakland Hills Oakland is a city in the East Bay region of the San Francisco Bay Area in the U.S. state of California. It is the county seat and most populous city in Alameda County, California, Alameda County, with a population of 440,646 in 2020. A major We ...
Berkeley Hills The Berkeley Hills are a range of the Pacific Coast Ranges, and overlook the northeast side of the valley that encompasses San Francisco Bay. They were previously called the "Contra Costa Range/Hills" (from the original Spanish ''Sierra de la Co ...
, several inland valleys, and
Mount Diablo Mount Diablo is a mountain of the Diablo Range, in Contra Costa County, California, Contra Costa County of the eastern San Francisco Bay Area in Northern California. It is south of Clayton, California, Clayton and northeast of Danville, Califo ...
, an isolated upthrust peak at the north end of the Diablo Range of hills. The summit of Mount Diablo is the origin of the Mount Diablo
Meridian Meridian or a meridian line (from Latin ''meridies'' via Old French ''meridiane'', meaning “midday”) may refer to Science * Meridian (astronomy), imaginary circle in a plane perpendicular to the planes of the celestial equator and horizon * ...
and Base Line, on which the surveys of much of California and western Nevada are based. The
Hayward Fault Zone The Hayward Fault Zone is a right-lateral strike-slip geologic fault zone capable of generating destructive earthquakes. The fault was first named in the Lawson Report of the 1906 San Francisco Earthquake in recognition of its involvement in the ...
runs through the western portion of the county, from Kensington to Richmond. The
Calaveras Fault The Calaveras Fault is a major branch of the San Andreas Fault System that is located in northern California in the San Francisco Bay Area. Activity on the different segments of the fault includes moderate and large earthquakes as well as aseis ...
runs in the south-central portion of the county, from Alamo to San Ramon. The
Concord Fault The Concord Fault is a geologic fault in the San Francisco Bay Area. The reason it is called that is because it is located under the city of Concord. It is connected to, and considered to be part of, the same fault zone as the Green Valley fault ...
runs through part of Concord and Pacheco, and the
Clayton-Marsh Creek-Greenville Fault The Clayton-Marsh Creek-Greenville Fault is a fault located in the eastern San Francisco Bay Area of California, in Alameda County and Contra Costa County. It is part of the somewhat parallel system of faults that are secondary to the San Andreas F ...
runs from Clayton at its north end to near Livermore. These strike-slip faults and the Diablo thrust fault near Danville are all considered capable of significantly destructive earthquakes and many lesser related faults are present in the area that cross critical infrastructure such as water, natural gas, and petroleum product pipelines, roads, highways, railroads, and BART rail transit.


Sub-areas

Contra Costa County is broadly divided into three sub-areas: * West County, including of the cities of El Cerrito, Richmond, San Pablo, Pinole, and Hercules, as well as the unincorporated communities of Kensington, El Sobrante, North Richmond, Rodeo, Crockett, and Port Costa. * Central County, which is itself further divided into three areas: ** Lamorinda, including of the cities of Lafayette, Moraga, and Orinda (the name being a portmanteau of the three cities' names), as well as the unincorporated area of Canyon. ** North Central County, including of the cities of Walnut Creek, Pleasant Hill, Concord, Clayton, and Martinez, as well as the unincorporated areas of Pacheco, Vine Hill, Clyde, the Pleasant Hill BART station, and Saranap. ** San Ramon Valley, including the cities of Danville and San Ramon, and the unincorporated communities of Alamo, Blackhawk, and Tassajara. * East County, on the western edge of the Central Valley, including of the cities of Pittsburg, Antioch, Oakley, and Brentwood, as well as the unincorporated communities of Bay Point, Bethel Island, Knightsen, Discovery Bay, and Byron.


Adjacent counties

*
Solano County Solano County () is a county located in the U.S. state of California. As of the 2020 census, its population was 453,491. The county seat is Fairfield. Solano County comprises the Vallejo–Fairfield metropolitan statistical area, which is a ...
- north *
Sacramento County Sacramento County () is a county located in the U.S. state of California. As of the 2020 United States census, the population was 1,585,055. Its county seat is Sacramento, which has been the state capital of California since 1854. Sacrament ...
- northeast *
San Joaquin County San Joaquin County ( ; , meaning " St. Joachim"), officially the County of San Joaquin, is a county located in the U.S. state of California. As of the 2020 United States census, the population was 779,233. The county seat is Stockton. San Jo ...
- east *
Alameda County Alameda County ( ) is a county located in the U.S. state of California. As of the 2020 census, the population was 1,682,353, making it the 7th-most populous county in the state and 21st most populous nationally. The county seat is Oakland. A ...
- south


National protected areas

*
Antioch Dunes National Wildlife Refuge Antioch Dunes National Wildlife Refuge is a sensitive sand dune habitat located near the city of Antioch, California on the south shore of the San Joaquin River-Stockton Deepwater Shipping Channel. It serves as a refuge for three endangered sp ...
*
Eugene O'Neill National Historic Site The Eugene O'Neill National Historic Site, located in Danville, California, preserves Tao House, the Monterey Colonial hillside home of America's only Nobel Prize-winning playwright, Eugene O'Neill. History of Tao House Eugene O'Neill had won ...
*
John Muir National Historic Site The John Muir National Historic Site is located in the San Francisco Bay Area, in Martinez, Contra Costa County, California. It preserves the 14-room Italianate Victorian mansion where the naturalist and writer John Muir lived, as well as a ne ...
*
Port Chicago Naval Magazine National Memorial The Port Chicago Naval Magazine National Memorial is a memorial dedicated in 1994 recognizing the dead of the Port Chicago disaster, and the critical role played by Port Chicago, California during World War II, in serving as the main facility ...
*
Rosie the Riveter/World War II Home Front National Historical Park Rosie the Riveter World War II Home Front National Historical Park is a United States national historical park National Historic Site (NHS) and National Historical Park (NHP) are designations for officially recognized areas of nationally hi ...


Mount Diablo

The most notable natural landmark in the county is the
Mount Diablo Mount Diablo is a mountain of the Diablo Range, in Contra Costa County, California, Contra Costa County of the eastern San Francisco Bay Area in Northern California. It is south of Clayton, California, Clayton and northeast of Danville, Califo ...
, at the northerly end of the
Diablo Range The Diablo Range is a mountain range in the California Coast Ranges subdivision of the Pacific Coast Ranges in northern California, United States. It stretches from the eastern San Francisco Bay Area at its northern end to the Salinas Valley a ...
. Mount Diablo and its neighboring North Peak are the centerpiece of Mt. Diablo State Park (MDSP), created legislatively in 1921 and rededicated in 1931 after land acquisitions had been completed. At the time this park comprised a very small portion of the mountain. In the 1960s, suburban development expanding from the surrounding valleys began to threaten the open space of the mountain. In 1971, MDSP consisted of . That year, concerned residents formed the non-profit organization Save Mount Diablo to raise funds and awareness to protect more open space. In addition to encouraging acquisition by the state and local authorities, SMD started fundraising and acquiring properties to transfer to the park. MDSP was the first of twenty-nine Diablo-area parks and preserves that have been created around the peaks; today these preserves protect more than . These Diablo public lands stretch southeast and include the
Concord Naval Weapons Station Concord Naval Weapons Station was a military base established in 1942 north of the city of Concord, California at the shore of the Sacramento River where it widens into Suisun Bay. The station functioned as a World War II armament storage de ...
, Shell Ridge Open Space and
Lime Ridge Open Space Lime most commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Bo ...
s near Walnut Creek, to the State Park, and east to the
Los Vaqueros Reservoir The Los Vaqueros Reservoir and watershed is located in the northern Diablo Range, within northeastern Contra Costa County, northern California. It was completed by the Contra Costa Water District (CCWD) in to improve the quality of drinking wat ...
watershed and four surrounding East Bay Regional Park District preserves, including
Morgan Territory Regional Preserve Morgan Territory Regional Preserve is a regional park in Contra Costa County, California. Located east of Clayton and north of Livermore, California, bordering on Mt. Diablo State Park, it is part of the East Bay Regional Park District (EBRPD). ...
,
Brushy Peak Regional Preserve Brushy Peak Regional Preserve is a regional park that is part of the East Bay Regional Park District, East Bay Regional Parks (EBRPD) and the Livermore Area Recreation and Park District (LARPD) systems. It is located in unincorporated land in Alame ...
,
Vasco Caves Regional Preserve Vasco Caves Regional Preserve is a natural and cultural protected area located on the eastern slope of Mount Diablo, on Vasco Road within eastern Contra Costa County, California. It was created to preserve wildlife habitats, California chaparral ...
, and
Round Valley Regional Preserve Round Valley Regional Preserve is a regional park just outside Antioch, CA and Brentwood, CA that is part of the East Bay Regional Parks (EBRPD) system. It is on Marsh Creek Road, approximately west of the intersection with Vasco Road. The pa ...
. The new Marsh Creek State Park, formerly known as Cowell Ranch State Park, and
Black Diamond Mines Regional Preserve The Black Diamond Mines Regional Preserve is a park located north of Mount Diablo in Contra Costa County, California under the administration of the East Bay Regional Park District (EBRPD). The district acquired the property in 1973. The pre ...
, are among the open spaces that stretch to the north. The open spaces controlled by cities, the East Bay Regional Park District, Mount Diablo State Park, and various regional preserves now adjoin and protect most of the elevated regions of the mountain. The name Mount Diablo is said to originate from an incident involving Spanish soldiers who christened a thicket as ''Monte del Diablo'' when natives they were pursuing apparently disappeared into the thicket. Anglo settlers later misunderstood the use of the word 'monte' (which can mean 'mountain', or 'thicket'), and applied the name to the most obvious local landmark. According to the ''Contra Costa Times'', in 2011, there were rumors that Contra Costa County was going to rename the mountain as "Mt. Ronald Reagan" or "Mt. Reagan", after the former US president and California governor. Residents have generated multiple petitions to change the name of the mountain, one in 2005 and another in 2011, but these were not successful.


Demographics


2020 census


2011


Places by population, race, and income


2010 Census

The 2010 United States Census reported that Contra Costa County had a population of 1,049,025. The racial makeup of Contra Costa County was 614,512 (58.6%)
White White is the lightest color and is achromatic (having no chroma). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully (or almost fully) reflect and scatter all the visible wa ...
; 97,161 (9.3%)
African American African Americans, also known as Black Americans and formerly also called Afro-Americans, are an Race and ethnicity in the United States, American racial and ethnic group that consists of Americans who have total or partial ancestry from an ...
; 6,122 (0.6%)
Native American Native Americans or Native American usually refers to Native Americans in the United States. Related terms and peoples include: Ethnic groups * Indigenous peoples of the Americas, the pre-Columbian peoples of North, South, and Central America ...
; 151,469 (14.4%) Asian (4.6% Filipino, 3.8% Chinese, 2.1% Indian); 4,845 (0.5%)
Pacific Islander Pacific Islanders, Pasifika, Pasefika, Pacificans, or rarely Pacificers are the peoples of the list of islands in the Pacific Ocean, Pacific Islands. As an ethnic group, ethnic/race (human categorization), racial term, it is used to describe th ...
; 112,691 (10.7%) from
other races Other often refers to: * Other (philosophy), a concept in psychology and philosophy Other or The Other may also refer to: Film and television * ''The Other'' (1913 film), a German silent film directed by Max Mack * ''The Other'' (1930 film), ...
; and 62,225 (5.9%) from two or more races. There were 255,560 people (24.4%) of
Hispanic The term Hispanic () are people, Spanish culture, cultures, or countries related to Spain, the Spanish language, or broadly. In some contexts, Hispanic and Latino Americans, especially within the United States, "Hispanic" is used as an Ethnici ...
or Latino ancestry, of any race; 17.1% of Contra Costa County's population was of
Mexican Mexican may refer to: Mexico and its culture *Being related to, from, or connected to the country of Mexico, in North America ** People *** Mexicans, inhabitants of the country Mexico and their descendants *** Mexica, ancient indigenous people ...
ancestry, while 1.9% was of
Salvadoran Salvadorans (), also known as Salvadorians, are citizens of El Salvador, a country in Central America. Most Salvadorans live in El Salvador, although there is also a significant Salvadoran diaspora, particularly in the United States, with smalle ...
heritage.


2000

As of the
census A census (from Latin ''censere'', 'to assess') is the procedure of systematically acquiring, recording, and calculating population information about the members of a given Statistical population, population, usually displayed in the form of stati ...
of 2000, there were 948,816 people, 344,129 households, and 242,266 families residing in the county. The population density was . There were 354,577 housing units at an average density of . Of residents who identified with European ethnicities, 9.0% were German, 7.7% Irish, 7.3% English, and 6.5% Italian ancestry according to Census 2000. 74.1% spoke English, 13.1% Spanish, and 2.6%
Tagalog Tagalog may refer to: Language * Tagalog language, a language spoken in the Philippines ** Old Tagalog, an archaic form of the language ** Batangas Tagalog, a dialect of the language * Tagalog script, the writing system historically used for Tagal ...
. By 2005, 53.2% of Contra Costa County's population were non-Hispanic whites. African Americans made up 9.6% of the population, while ethnic Asians constituted 13.1%. Latinos, representing people of Spanish, Portuguese, indigenous and mestizo populations of the Western hemisphere, comprised 21.1% of the county population. In 2000, there were 344,129 households, out of which 35.4% had children under the age of 18 living with them, 54.5% were married couples living together, 11.5% had a female householder with no husband present, and 29.6% were non-families. 22.9% of all households were made up of individuals, and 8.00% had someone living alone who was 65 years of age or older. The average household size was 2.72 and the average family size was 3.23. In the county, the population was spread out, with: * 26.5% under the age of 18 * 7.7% from 18 to 24 * 30.6% from 25 to 44 * 23.9% from 45 to 64 * 11.3% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 95.4 males. For every 100 females age 18 and over, there were 92.2 males. The median income for a household in the county was $63,675, and the median income for a family was $73,039 (these figures had risen to $75,483 and $87,435 respectively as of a 2007 estimate). Males had a median income of $52,670 versus $38,630 for females. The
per capita income Per capita income (PCI) or average income measures the average income earned per person in a given area (city, region, country, etc.) in a specified year. In many countries, per capita income is determined using regular population surveys, such ...
for the county was $30,615. About 5.4% of families and 7.6% of the population were below the
poverty line The poverty threshold, poverty limit, poverty line, or breadline is the minimum level of income deemed adequate in a particular country. The poverty line is usually calculated by estimating the total cost of one year's worth of necessities for ...
, including 9.8% of those under age 18 and 6.0% of those age 65 or over. In 2000, the largest denominational groups were
Catholics The Catholic Church (), also known as the Roman Catholic Church, is the largest Christian church, with 1.27 to 1.41 billion baptized Catholics worldwide as of 2025. It is among the world's oldest and largest international institut ...
(with 204,070 adherents) and
Evangelical Protestant Evangelicalism (), also called evangelical Christianity or evangelical Protestantism, is a worldwide, interdenominational movement within Protestant Christianity that emphasizes evangelism, or the preaching and spreading of the Christian ...
s (with 74,449 adherents). The largest religious bodies were the Catholic Church (with 204,070 members) and The
Baptist General Conference Converge, formerly the Baptist General Conference (BGC) and Converge Worldwide, is a Baptist Christian denomination in the United States. It is affiliated with the Baptist World Alliance and the National Association of Evangelicals. The headquart ...
(with 24,803 members). The
Rohr Jewish Learning Institute The Rohr Jewish Learning Institute (JLI) is a division of Merkos L'Inyonei Chinuch, the educational arm of the Chabad-Lubavitch Orthodox Jewish Hasidic dynasty. It offers adult Jewish courses on Jewish history, law, ethics, philosophy and ...
teaches courses in the county.


Politics

Since 1932, Contra Costa County has been a Democratic stronghold in presidential elections. It temporarily leaned toward the Republican Party in the 1970s and 1980s, with successive presidential wins by
Richard Nixon Richard Milhous Nixon (January 9, 1913April 22, 1994) was the 37th president of the United States, serving from 1969 until Resignation of Richard Nixon, his resignation in 1974. A member of the Republican Party (United States), Republican ...
in 1972,
Gerald Ford Gerald Rudolph Ford Jr. (born Leslie Lynch King Jr.; July 14, 1913December 26, 2006) was the 38th president of the United States, serving from 1974 to 1977. A member of the Republican Party (United States), Republican Party, Ford assumed the p ...
in 1976, and
Ronald Reagan Ronald Wilson Reagan (February 6, 1911 – June 5, 2004) was an American politician and actor who served as the 40th president of the United States from 1981 to 1989. He was a member of the Republican Party (United States), Republican Party a ...
in 1980 and 1984. Reagan was the last Republican presidential candidate to win the county. In the
United States House of Representatives The United States House of Representatives is a chamber of the Bicameralism, bicameral United States Congress; it is the lower house, with the U.S. Senate being the upper house. Together, the House and Senate have the authority under Artic ...
, Contra Costa County is split among three congressional districts: * * * In the
State Assembly State Assembly is the name given to various legislatures, especially lower houses or full legislatures in states in federal systems of government. Channel Islands States Assembly is the name of the legislature of the Bailiwick of Jersey. The Baili ...
, Contra Costa County is split among four districts: * * * * In the
State Senate In the United States, the state legislature is the legislative branch in each of the 50 U.S. states. A legislature generally performs state duties for a state in the same way that the United States Congress performs national duties at ...
, the county is split among three districts: * * * Democrats hold wide advantages in voter registration numbers in all political subdivisions in Contra Costa County. The Democrats' largest registration advantage in Contra Costa is in the cities of
Richmond Richmond most often refers to: * Richmond, British Columbia, a city in Canada * Richmond, California, a city in the United States * Richmond, London, a town in the London Borough of Richmond upon Thames, England * Richmond, North Yorkshire, a town ...
, where there is a 60.3% registration advantage with 3,192 Republicans (6.2%) out of 51,395 registered voters compared to 34,159 Democrats (66.5%) and 12,095 voters who have no party preference (23.5%); El Cerrito, where there is a 59.0% registration advantage with 1,169 Republicans (7.4%) out of 15,877 registered voters compared to 10,543 Democrats (67.6%) and 3,654 voters who have no party preference (23.0%); and San Pablo, where there is a 58.3% registration advantage with 641 Republicans (6.1%) out of 10,550 registered voters compared to 6,793 Democrats (64.4%) and 2,746 voters who have no party preference (26.0%).


Voter registration statistics


Cities by population and voter registration


Crime

The following table includes the number of incidents reported and the rate per 1,000 persons for each type of offense.


Cities by population and crime rates (2019)


Economy


Agriculture

The great rancheros of the Spanish period were divided and sold for agricultural uses, with intensively irrigated farming made possible in some areas by the development of canals that brought water from the eastern riverside portions of the county to the central portion. Other areas could use the more limited water available from local creeks and from wells. Orchards dominated where such water was available, while other, seasonally dry areas were used for cattle ranching. In central parts of the county walnuts were an especially attractive orchard crop, using the thin-shelled English Walnut branches grafted to the hardy and disease-resistant American Walnut root stock. In the Moraga region, pears dominated, and many old (but untended) roadside trees are still picked seasonally by passers-by. In eastern county, stone fruit, especially cherries, is still grown commercially, with seasonal opportunities for people to pick their own fruit for a modest fee.


Irrigation canals

The Contra Costa Canal, a concrete-lined and fenced irrigation canal still makes a loop through central county and provided industrial and agricultural grade water to farms and industry. While no longer used for extensive irrigation, it is still possible for adjoining landowners (now large suburban lot owners) to obtain pumping permits. Most of this water is destined for the heavy industry near Martinez. As with the railroad rights of way there is now an extensive public trail system along these canals.


Commuter railroads

The development of commuter railroads proceeded together with the subdivision of farms into parcels. In some cases, such as the development of
Saranap Saranap (until 1913, Dewing Park) is a residential census-designated place (CDP) within central Contra Costa County, California. Lying at an elevation of 180 feet (55 m), it is bounded on the south and east by portions of Walnut Creek (including ...
, the same developer controlled both the railroad (
Sacramento Northern The Sacramento Northern Railway (reporting mark SN) was a electric interurban railway that connected Chico in northern California with Oakland via the state capital, Sacramento. In its operation it ran directly on the streets of Oakland, Sacr ...
) and the development. These early suburbanization developments were an extension of the earlier development of
trolley car suburb A streetcar suburb is a residential community whose growth and development was strongly shaped by the use of streetcar lines as a primary means of transportation. Such suburbs developed in the United States in the years before the automobile, when ...
s in what are now considered the highly urban environments of the near East Bay.


Heavy industry

Owing to its extensive waterfront on
San Francisco San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...
, San Pablo, and Suisun bays the northwestern and northern segments have long been sites for heavy industry, including a number of still active
oil refineries An oil refinery or petroleum refinery is an industrial process plant where petroleum (crude oil) is transformed and refined into products such as gasoline (petrol), diesel fuel, asphalt base, fuel oils, heating oil, kerosene, liquefied pet ...
(particularly
Chevron Chevron (often relating to V-shaped patterns) may refer to: Science and technology * Chevron (aerospace), sawtooth patterns on some jet engines * Chevron (anatomy), a bone * '' Eulithis testata'', a moth * Chevron (geology), a fold in rock la ...
in Richmond, Phillips 66 in
Rodeo Rodeo () is a competitive equestrian sport that arose out of the working practices of cattle herding in Spain and Mexico, expanding throughout the Americas and to other nations. It was originally based on the skills required of the working vaqu ...
, Shell Oil (now PBF) and Tesoro (now Marathon)- in Martinez), chemical plants (
Dow Chemical The Dow Chemical Company is an American multinational corporation headquartered in Midland, Michigan, United States. The company was among the three largest chemical producers in the world in 2021. It is the operating subsidiary of Dow Inc., ...
) and a once substantial integrated steel plant,
United States Steel The United States Steel Corporation is an American steel company based in Pittsburgh, Pennsylvania. It maintains production facilities at several additional locations in the U.S. and Central Europe. The company produces and sells steel products, ...
, now reduced to secondary production of strip sheet and wire. The
San Joaquin River The San Joaquin River ( ; ) is the longest river of Central California. The long river starts in the high Sierra Nevada and flows through the rich agricultural region of the northern San Joaquin Valley before reaching Suisun Bay, San Francis ...
forms a continuation of the northern boundary turns southward to form the eastern boundary of the county. Some substantial Sacramento-San Joaquin Delta "islands" (actually leveed former marshes) are included in this corner of the county.


Housing


West County

The West County is the area near or on San Francisco and San Pablo bays. The housing stock in the region was extensively developed after the great San Francisco earthquake of 1906. Much of the housing stock in these areas is becoming quite expensive. As an alternative to moving to either the expensive central county, or the too-distant East County, this area is becoming
gentrified Gentrification is the process whereby the character of a neighborhood changes through the influx of more affluent residents (the "gentry") and investment. There is no agreed-upon definition of gentrification. In public discourse, it has been us ...
, with a mix of races and income levels — a character actively sought by some housing purchasers. The downside of this is a corresponding lack of affordable housing for those working lower-paying service jobs — a problem endemic throughout the region. There has recently been a housing boom or tract housing in
Richmond Richmond most often refers to: * Richmond, British Columbia, a city in Canada * Richmond, California, a city in the United States * Richmond, London, a town in the London Borough of Richmond upon Thames, England * Richmond, North Yorkshire, a town ...
and also in the
Hercules Hercules (, ) is the Roman equivalent of the Greek divine hero Heracles, son of Jupiter and the mortal Alcmena. In classical mythology, Hercules is famous for his strength and for his numerous far-ranging adventures. The Romans adapted the Gr ...
areas. These gentrifying areas are the most diverse in Contra Costa County.


Central county

The central part of the county is a valley traversed by Interstate 680 and Highway 24. The towns east of the hills, on or near Highway 24 and their surrounding areas ( Lafayette, Moraga and
Orinda Orinda is a city in Contra Costa County, California, United States. The city's population as of the 2020 census is estimated at 19,514 residents. History Orinda is located within four Mexican land grants: Rancho Laguna de los Palos Colorado ...
) are collectively known as ''Lamorinda''. The major central county cities along Interstate 680 are Martinez, Concord, Pleasant Hill, Walnut Creek, Danville, San Ramon, and unincorporated Alamo. Owing to the high quality of its public schools (due largely to both demographics and added support from prosperous parents), this area has become a magnet for well–off families with children. During the real estate boom, housing prices were driven to astounding levels. From 2007, home prices in the region have seen substantial decreases and the affordability rate has risen. During the real estate boom, the high price of homes and scarcity of land resulted in many speculators purchasing older, smaller homes and partially or completely tearing them down to construct larger homes. In this way the central county region has become a mix of older suburbs, newer developments, small lot "infill" developments, and extensive shopping areas.


East County

Lower cost modern tract developments continue along
Suisun Bay Suisun Bay ( ; Wintun for "where the west wind blows") is a shallow tidal estuary (a northeastern extension of the San Francisco Bay) in Northern California. It lies at the confluence of the Sacramento River and San Joaquin River, forming the e ...
in the "East County" towns of
Pittsburg Pittsburg may refer to: Places United States Cities, towns, townships and counties *Pittsburg, California * Pittsburg, Florida *Pittsburg, Kansas, Crawford County *Pittsburg, New Hampshire * Pittsburg, Oklahoma *Pittsburg, Texas *Pittsburg Coun ...
,
Antioch Antioch on the Orontes (; , ) "Antioch on Daphne"; or "Antioch the Great"; ; ; ; ; ; ; . was a Hellenistic Greek city founded by Seleucus I Nicator in 300 BC. One of the most important Greek cities of the Hellenistic period, it served as ...
, and Oakley - new "bedroom" communities" to serve the now "edge cities". The median income of a family in the two relatively affluent East County towns of Brentwood and
Discovery Bay Discovery Bay is a picturesque residential community located on Lantau Island. The 2021 census recorded a population of 19,336 residents in DB, with 55% of them being non-Chinese. DB is home to a significant community compared of expatriates ...
is approaching $100k/yr. placing them in the top fifteen percent of affluent towns in the United States. California Distinguished Schools, golf courses, vineyards, and upscale homes are found in Brentwood and Discovery Bay. Discovery Bay is based on a waterfront community of 3,500+ homes with private docks with access to the Sacramento-San Joaquin River Delta. Discovery Bay also features gated and non-gated "off-water" communities with homes from up to . From 2010 to 2018 Highway 4 underwent multimillion-dollar improvements from that added lanes through Brentwood, Antioch and Pittsburg to reduce driving time between East County and Concord/Walnut Creek, as this commute at one time was the 10th worst in the nation.
Vasco Road Vasco Road is a roadway over the Diablo Range that connects Livermore and Brentwood, California. Although it is not part of the California State Highway system, it is the principal north–south commuter route serving eastern Alameda and Co ...
is also an important link between East County/Brentwood and Livermore. Additionally, a county road from Brentwood to Tracy has received Federal Funds to be upgraded to a highway link between the areas.


County budget problems

Across 30 years, two forces combined to create county budget problems, peaking in 2008. First, rather than compensate police, medical, and firefighting personnel directly, health and retirement benefits were granted without proper actuarial examination, leading to unexpected but predictable high costs as personnel aged and ultimately retired with continued "first class" health and retirement benefits. Second, the collapse of the "housing bubble" enabled purchasers of distressed properties — many of which were owned by banks and other mortgage holders — to petition for lower property assessments, in many cases reducing by half the revenue to the county for specific parcels. Continuing downturns in employment prospects further increased the needs for various social services. These deficits and demands, combined with a lack of support from a similarly stressed California state government and the United States Federal government, required county supervisors and service providers to allocate limited resources in a time of increasing demand. The projected budget deficit was $45 million as of early 2011. Perhaps more significantly, the total unfunded liability for retiree benefits is $2.4 billion.


Technical innovators

In the 1970s and 1980s, many small and innovative technical firms started in Contra Costa. Most of these are no longer present, either failing, being absorbed into larger corporations, or outgrowing their original location and moving elsewhere in the Bay Area.


Corporate headquarters

By the early 1990s, 22 million square feet of office space had been built along the ''680 corridor'', that segment of Interstate Highway 680 that extends from
Concord Concord may refer to: Meaning "agreement" * Harmony, in music * Agreement (linguistics), a change in the form of a word depending on grammatical features of other words Arts and media * ''Concord'' (video game), a defunct 2024 first-person sh ...
in the north to San Ramon in the south, continuing into inland
Alameda County Alameda County ( ) is a county located in the U.S. state of California. As of the 2020 census, the population was 1,682,353, making it the 7th-most populous county in the state and 21st most populous nationally. The county seat is Oakland. A ...
from
Dublin Dublin is the capital and largest city of Republic of Ireland, Ireland. Situated on Dublin Bay at the mouth of the River Liffey, it is in the Provinces of Ireland, province of Leinster, and is bordered on the south by the Dublin Mountains, pa ...
to Pleasanton. During the 1980s and early 1990s, many corporations that were formerly housed in the more central metropolitan area followed their employees by moving to these large suburban and edge city office areas and office parks.


Redevelopment

There are currently political fights over the potential redevelopment of the county seat ( Martinez), with long-term residents and many elsewhere in the county concerned that it will lose its remaining small-town charm and utility in an effort to become more like the county's major recreational shopping center of Walnut Creek. The inland portions of the
Concord Naval Weapons Station Concord Naval Weapons Station was a military base established in 1942 north of the city of Concord, California at the shore of the Sacramento River where it widens into Suisun Bay. The station functioned as a World War II armament storage de ...
have been declared surplus by the Federal government and this area is expected to provide what is likely the last opportunity to plan and build city-sized development within the central county. This area will become a portion of the city of Concord, and planners expect that development will be confined to the lower and flatter portions of the depot, with the remainder becoming a substantial addition to the county's open space. Much of the land to be developed is relatively flat grassland and the most prominent structures are ammunition bunkers that will be removed, so future uses of the property are largely unconstrained by previous uses.


Education

The Contra Costa Community College District is a community college district that encompasses three community colleges:
Contra Costa College Contra Costa College is a public community college in San Pablo, California, United States. It is the west campus of the Contra Costa Community College District. It is part of the California community colleges system, one of the three college s ...
,
Diablo Valley College Diablo Valley College (DVC) is a public community college with campuses in Pleasant Hill and San Ramon in Contra Costa County, California. DVC is one of three public community colleges in the Contra Costa Community College District (along with ...
, and
Los Medanos College Los Medanos College (LMC) is a public community college in Pittsburg, California, United States. It was established in 1974 and is part of the Contra Costa Community College District. LMC also has had an extension in Brentwood since 1998 ca ...
. The
Contra Costa County Library The Contra Costa County Library is the public library system in Contra Costa County, California, United States. There are 26 community libraries including the NRHP-listed Martinez Library, access to electronic information via a website, over 4 ...
is the county's library system. K-12 school districts in the county:
Text list
/ref> *
Antioch Unified School District The Antioch Unified School District serves approximately 17,000 students in the city of Antioch, California, and a portion of the neighboring city of Oakley. History The Antioch Unified School District was formed in 1921 from the Antioch and ...
* John Swett Unified School District *
Livermore Valley Joint Unified School District Livermore Valley Joint Unified School District (LVJUSD) is a public school district located in Livermore, California, United States. It is located in Alameda County. , the superintendent is Torie Gibson, and the school board is composed of Stev ...
*
Martinez Unified School District The Martinez Unified School District (MUSD) is a public school district in Contra Costa County, California. It currently serves over 4,000 students and operates 4 elementary schools, one middle school and one high school, with two alternative sc ...
*
Mount Diablo Unified School District Mount Diablo Unified School District (MDUSD) is a public school district in Contra Costa County, California. It currently operates 29 elementary schools, 9 middle schools, and 5 high schools, with 7 alternative school An alternative schoo ...
* Pittsburg Unified School District *
San Ramon Valley Unified School District The San Ramon Valley Unified School District (SRVUSD) is a public school district in Contra Costa County, California. It has 36 school sites serving more than 32,000 students within the communities of Alamo, Danville, Blackhawk, Diablo, and ...
*
West Contra Costa Unified School District The West Contra Costa Unified School District (WCCUSD; formerly known as Richmond School District) is the school district for western Contra Costa County, California. It is based in Richmond, California. In addition to Richmond, the district ...
Secondary school districts in the county: *
Acalanes Union High School District Acalanes Union High School District is a public union high school district, high school district in Contra Costa County, located in the Bay Area of California. The district takes its name from Rancho Acalanes, an 1834 ranchos of California, Me ...
*
Liberty Union High School District Liberty Union High School District is a public school district based in northeastern Contra Costa County, California. The district serves approximately 8200 students from grades 9-12. The communities it serves include Brentwood, the majority ...
Elementary school districts in the county: *
Brentwood Union Elementary School District Brentwood Union School District is a public school district based in Contra Costa County, California. The district serves approximately 9700 students from grades K–8. It includes almost all of Brentwood and portions of Antioch and Oakley. ...
*
Byron Union Elementary School District Byron Union School District is a public school district based in Contra Costa County, California. It serves the communities of Byron and Discovery Bay. Text list/ref> It feeds into Liberty Union High School District Liberty Union High Sc ...
* Canyon Elementary School District *
Knightsen Elementary School District Knightsen Elementary School District is a public school district based in Contra Costa County, California. The district serves approximately 600 students from grades K–8. It includes almost all of Knightsen and portions of Brentwood and O ...
*
Lafayette Elementary School District Lafayette Elementary School District is a public school district based in Contra Costa County, California, United States. Schools Elementary * Burton Valley Elementary * Happy Valley Elementary * Lafayette Elementary * Spring Hill E ...
*
Moraga Elementary School District The Moraga School District is an elementary school district in Moraga, California. The majority of Moraga is within this district. Schools in the district include Joaquin Moraga Intermediate School, Camino Pablo Elementary School, Donald Rhee ...
*
Oakley Union Elementary School District Oakley Union Elementary School District is a public school district in Contra Costa County, California, United States. The district serves approximately 5000 students from grades K–8. It includes most of Oakley, all of Bethel Island, and p ...
*
Orinda Union Elementary School District Orinda Union School District (OUSD) is a school district in Orinda, California, United States, that serves students in Transitional Kindergarten (TK) through 8th grade. It consists of four elementary schools and one middle school. It is the hig ...
*
Walnut Creek Elementary School District Walnut Creek Elementary School District is a public school district based in Walnut Creek, California, United States. The district serves approximately 3,500 students from grades K–8. It serves portions of Walnut Creek. Text list/ref> It ...


Media

Contra Costa County receives media from the rest of the Bay Area. The City of Concord is served by the daily newspaper, the ''
East Bay Times The ''East Bay Times'' is a daily broadsheet newspaper based in Walnut Creek, California, United States, owned by the Bay Area News Group (BANG), a subsidiary of Media News Group, that serves Contra Costa County, California, Contra Costa and Al ...
'' published by the Bay Area News Group-East Bay (part of the
Media News Group MNG Enterprises, Inc., doing business as Digital First Media and MediaNews Group, is a Denver, Colorado, United States–based newspaper publisher owned by Alden Global Capital. As of May 2021, it owns over 100 newspapers and 200 assorted othe ...
, Denver, Colorado), with offices in Walnut Creek. The paper was originally a paper run and owned by the Lesher family. Since the death of Dean Lesher in 1993, the paper has had several owners. The publisher also issues weekly local papers, such as the ''Concord Transcript,'' which is the local paper for Concord and nearby Clayton. In December 2019, there was a flurry of reports from reliable sources including the
Associated Press The Associated Press (AP) is an American not-for-profit organization, not-for-profit news agency headquartered in New York City. Founded in 1846, it operates as a cooperative, unincorporated association, and produces news reports that are dist ...
and the
San Francisco Chronicle The ''San Francisco Chronicle'' is a newspaper serving primarily the San Francisco Bay Area of Northern California. It was founded in 1865 as ''The Daily Dramatic Chronicle'' by teenage brothers Charles de Young and M. H. de Young, Michael H. ...
that the 161-year-old Martinez News-Gazette, one of the longest-running newspapers in California, may have to cease publication. But as of late May 2020, the threatened cessation did not materialize and the newspaper appears to have weathered that storm. The newspaper did cease publication of a print edition effective April 2, 2020, but this was characterized as a temporary measure arising from a lack of advertising revenue. Since March 2020, this in turn arose as many local businesses were forced to suspended operations or even ceased to exist, when the area was under
shelter-in-place Shelter-in-place (SIP; also known as a shelter-in-place warning, SAME code SPW) is the act of seeking safety within the building one already occupies, rather than evacuating the area or seeking a community emergency shelter. The American Red Cr ...
regulations arising from
COVID-19 pandemic The COVID-19 pandemic (also known as the coronavirus pandemic and COVID pandemic), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), began with an disease outbreak, outbreak of COVID-19 in Wuhan, China, in December ...
. The newspaper plans to resume a full print edition when the local shelter-in-place restrictions are lifted.


Transportation

Prior to 1903, most travel to central Contra Costa County was by boat or rail to Martinez on the northern waterfront and from there to the industrial areas east along the waterfront as well as farming regions to the south. In 1903, the first tunnel through the Oakland hills (now Old Tunnel Road) was built, principally as a means of bringing
hay Hay is grass, legumes, or other herbaceous plants that have been cut and dried to be stored for use as animal fodder, either for large grazing animals raised as livestock, such as cattle, horses, goats, and sheep, or for smaller domesticate ...
by horse-, mule-, or ox-drawn wagons from central and eastern agricultural areas to feed the
draft animal A working animal is an animal, usually domesticated, that is kept by humans and trained to perform tasks. Some are used for their physical strength (e.g. oxen and draft horses) or for transportation (e.g. riding horses and camels), while othe ...
s that provided the power to public and private transportation in the East Bay at the time. The tunnel exited in the hills high above the crossroads of
Orinda Orinda is a city in Contra Costa County, California, United States. The city's population as of the 2020 census is estimated at 19,514 residents. History Orinda is located within four Mexican land grants: Rancho Laguna de los Palos Colorado ...
with the road continuing on to Lafayette, Walnut Creek, and Danville. The road was just wide enough for one car in each direction and had no shoulders. In 1937, the two-bore
Caldecott Tunnel The Caldecott Tunnel is a four-bore highway tunnel through the Berkeley Hills between Oakland and Orinda, California. Its four bores carry California State Route 24. Named after Thomas E. Caldecott, former mayor of Berkeley, it opened in ...
for road vehicles was completed, making interior Contra Costa County much more accessible. After World War II, the tunnels allowed waves of development to proceed, oriented toward
Oakland Oakland is a city in the East Bay region of the San Francisco Bay Area in the U.S. state of California. It is the county seat and most populous city in Alameda County, with a population of 440,646 in 2020. A major West Coast port, Oakland is ...
rather than the northern shoreline, and the northern shoreline cities began to decline. The tunnel has since been augmented with a third bore, completed in 1964, and a fourth, completed in 2013.


Major highways

*
Interstate 80 Interstate 80 (I-80) is an east–west transcontinental freeway that crosses the United States from San Francisco, California, to Teaneck, New Jersey, in the New York metropolitan area. The highway was designated in 1956 as one of the ori ...
* Interstate 580 * Interstate 680 * State Route 4 * State Route 24 * State Route 123 (San Pablo Avenue) – formerly
U.S. Route 40 U.S. Route 40 or U.S. Highway 40 (US 40), also known as the Main Street of America (a nickname shared with U.S. Route 66), is a major east–west United States Highway traveling across the United States from the Mountain States to the Mid- ...
* State Route 160 * State Route 242


Mass transit

*
Amtrak The National Railroad Passenger Corporation, Trade name, doing business as Amtrak (; ), is the national Passenger train, passenger railroad company of the United States. It operates intercity rail service in 46 of the 48 contiguous United Stat ...
runs its ''
San Joaquins The ''San Joaquins'' is a state-supported passenger train service operated by Amtrak in California's San Joaquin Valley. As of 2025, the service operates seven daily round trips between its southern terminus at Bakersfield and Stockton. Of the ...
'' line to
Southern California Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural List of regions of California, region that generally comprises the southern portion of the U.S. state of California. Its densely populated coastal reg ...
and its ''
Capitol Corridor The ''Capitol Corridor'' is a passenger train route in Northern California operated by Amtrak between San Jose, California, San Jose, in the Bay Area, and Auburn, California, Auburn, in the Sacramento Valley. The route is named after the two ...
'' line to
Sacramento Sacramento ( or ; ; ) is the capital city of the U.S. state of California and the seat of Sacramento County. Located at the confluence of the Sacramento and American Rivers in Northern California's Sacramento Valley, Sacramento's 2020 p ...
and San Jose through stations in Richmond, Martinez, and Antioch-Pittsburg. *
BART Bay Area Rapid Transit (BART) is a rapid transit system serving the San Francisco Bay Area in California. BART serves List of Bay Area Rapid Transit stations, 50 stations along six routes and of track, including eBART, a spur line running t ...
, a high-speed
commuter rail Commuter rail or suburban rail is a Passenger train, passenger rail service that primarily operates within a metropolitan area, connecting Commuting, commuters to a Central business district, central city from adjacent suburbs or commuter town ...
system, functions as the Bay Area's metro system. **
eBART eBART (East Contra Costa County BART extension) is a hybrid rail (light rail with some features similar to commuter rail) branch line of the Bay Area Rapid Transit (BART) system in eastern Contra Costa County, California, United States. The lin ...
(East Contra Costa County BART extension) is designed to bring
rapid transit Rapid transit or mass rapid transit (MRT) or heavy rail, commonly referred to as metro, is a type of high-capacity public transport that is generally built in urban areas. A grade separation, grade separated rapid transit line below ground su ...
services along the Highway 4 corridor. *
AC Transit AC Transit is the main Public transport bus service, bus transit operator in the East Bay region of the San Francisco Bay Area, California. AC Transit is the third largest bus operator in California, serving the western portions of Alameda and C ...
provides local service in West County and in Orinda, in addition to western Alameda County, Transbay commuter services to
San Francisco San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...
, bus rapid transit lines and the bulk of All Nighter service for the
East Bay The East Bay is the eastern region of the San Francisco Bay Area and includes cities along the eastern shores of San Francisco Bay and San Pablo Bay. The region has grown to include inland communities in Alameda and Contra Costa counties. Wi ...
. *
County Connection The County Connection (officially, the Central Contra Costa Transit Authority, CCCTA) is a Concord-based public transit agency operating fixed-route bus and ADA paratransit (County Connection LINK) service in and around central Contra Costa Co ...
provides local service in Central C.C. County and connecting services to Dublin and Pittsburg. *
Tri-Delta Transit Tri Delta Transit, formally the Eastern Contra Costa Transit Authority, is a joint powers agency (JPA) of the governments of Pittsburg, Antioch, Oakley, Brentwood, and Contra Costa County that provides bus service for the eastern area of Contra ...
provides local bus service in East C.C. County and connecting regional services to Martinez, Livermore, and Stockton. *
WestCAT WestCAT is a public transportation service in western Contra Costa County (north of Alameda County, California, Alameda County). It is a service of the Western Contra Costa Transit Authority. Contra Costa County has four public bus transportation ...
provides local bus service in northern West C.C. County with connecting service to BART and transbay service to the city (San Francisco). *
Golden Gate Transit Golden Gate Transit (GGT) is a public transportation system serving the North Bay region of the San Francisco Bay Area in California, United States. It primarily serves Marin County, Sonoma County, and San Francisco, and also provides limited ser ...
provides connecting transbay service between
Marin County Marin County ( ) is a county located in the northwestern part of the San Francisco Bay Area of the U.S. state of California. As of the 2020 census, the population was 262,231. Its county seat and largest city is San Rafael. Marin County is ac ...
and
Richmond Richmond most often refers to: * Richmond, British Columbia, a city in Canada * Richmond, California, a city in the United States * Richmond, London, a town in the London Borough of Richmond upon Thames, England * Richmond, North Yorkshire, a town ...
and El Cerrito del Norte BART stations via the Richmond-San Rafael Bridge. *
Vallejo Transit SolTrans, officially Solano County Transit, is a joint powers authority that provides public transportation service to the southern Solano County cities of Vallejo and Benicia, California, United States. SolTrans was established in 2011 and i ...
and
Fairfield and Suisun Transit Fairfield Transit (FAST) provides general public fixed route bus service through eight local routes. All FAST buses are wheelchair accessible and most are equipped with bike racks. In , the system had a ridership of , or about per weekday as of ...
provide regional feeder service to El Cerrito del Norte BART from
Solano County Solano County () is a county located in the U.S. state of California. As of the 2020 census, its population was 453,491. The county seat is Fairfield. Solano County comprises the Vallejo–Fairfield metropolitan statistical area, which is a ...
. * Benicia Transit provides commuter service between the Vallejo Ferry Terminal and BART in Concord through
Benicia Benicia ( , ) is a city in Solano County, California, located on the north bank of the Carquinez Strait in the North Bay region of the San Francisco Bay Area. It served as the capital of California for nearly thirteen months from 1853 to 1854. ...
in Solano County.


Airports

The county has two general aviation airports: *
Buchanan Field Airport Buchanan Field Airport is a medium-sized general and business public airport in Contra Costa County, California, United States, one mile west of the center of Concord and just east of Pacheco in the San Francisco Bay Area. The airport's str ...
, located in
Concord Concord may refer to: Meaning "agreement" * Harmony, in music * Agreement (linguistics), a change in the form of a word depending on grammatical features of other words Arts and media * ''Concord'' (video game), a defunct 2024 first-person sh ...
*
Byron Airport Byron Airport is a public airport two miles south of Byron, in Contra Costa County, California, United States. The FAA's National Plan of Integrated Airport Systems for 2007–2011 categorized it as a ''reliever airport''. About On the lee sid ...
, located south of
Byron George Gordon Byron, 6th Baron Byron (22 January 1788 – 19 April 1824) was an English poet. He is one of the major figures of the Romantic movement, and is regarded as being among the greatest poets of the United Kingdom. Among his best-kno ...
JetSuiteX JetSuiteX, Inc. (commonly known as JSX) is an American air carrier in the United States and Mexico that describes itself as a "hop-on jet service" that operates point-to-point flights between and within Arizona, California, Colorado, Florida, ...
provides four times weekly service from Concord Airport (CCR) to Las Vegas, Burbank, and Santa Ana.


Railroads

The western termini of several original transcontinental railroad routes have been located in
Oakland Oakland is a city in the East Bay region of the San Francisco Bay Area in the U.S. state of California. It is the county seat and most populous city in Alameda County, with a population of 440,646 in 2020. A major West Coast port, Oakland is ...
, in
Alameda County Alameda County ( ) is a county located in the U.S. state of California. As of the 2020 census, the population was 1,682,353, making it the 7th-most populous county in the state and 21st most populous nationally. The county seat is Oakland. A ...
, including
Union Pacific The Union Pacific Railroad is a Class I freight-hauling railroad that operates 8,300 locomotives over routes in 23 U.S. states west of Chicago and New Orleans. Union Pacific is the second largest railroad in the United States after BNSF, ...
,
Southern Pacific The Southern Pacific (or Espee from the railroad initials) was an American Class I railroad network that existed from 1865 to 1996 and operated largely in the Western United States. The system was operated by various companies under the names ...
, and Santa Fe railroads. From Oakland, there are two primary routes east: *The former Southern Pacific (originally
Central Pacific Railroad The Central Pacific Railroad (CPRR) was a rail company chartered by U.S. Congress in 1862 to build a railroad eastwards from Sacramento, California, to complete most of the western part of the "First transcontinental railroad" in North Americ ...
) line north through
Richmond Richmond most often refers to: * Richmond, British Columbia, a city in Canada * Richmond, California, a city in the United States * Richmond, London, a town in the London Borough of Richmond upon Thames, England * Richmond, North Yorkshire, a town ...
, closely hugging the
San Pablo Bay San Pablo Bay is a tidal estuary that forms the northern extension of the San Francisco Bay in the East Bay and North Bay regions of the San Francisco Bay Area in northern California. Most of the Bay is shallow; however, there is a deep wate ...
coastline to Martinez, where it crosses
Suisun Bay Suisun Bay ( ; Wintun for "where the west wind blows") is a shallow tidal estuary (a northeastern extension of the San Francisco Bay) in Northern California. It lies at the confluence of the Sacramento River and San Joaquin River, forming the e ...
on a drawbridge before proceeding to
Sacramento Sacramento ( or ; ; ) is the capital city of the U.S. state of California and the seat of Sacramento County. Located at the confluence of the Sacramento and American Rivers in Northern California's Sacramento Valley, Sacramento's 2020 p ...
and the crossing of the
Sierra Nevada The Sierra Nevada ( ) is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primari ...
via Donner *The former
Western Pacific Railroad The Western Pacific Railroad was a Class I railroad in the United States. It was formed in 1903 as an attempt to break the near-monopoly the Southern Pacific Railroad had on rail service into northern California. WP's Feather River Route dire ...
line, which runs east through Niles Canyon, Livermore and over
Altamont Pass Altamont Pass, formerly Livermore Pass, is a low mountain pass in the Diablo Range of Northern California between Livermore in the Livermore Valley and Tracy in the San Joaquin Valley. The name is actually applied to two distinct but nea ...
, en route in a north-easterly direction to
Sacramento Sacramento ( or ; ; ) is the capital city of the U.S. state of California and the seat of Sacramento County. Located at the confluence of the Sacramento and American Rivers in Northern California's Sacramento Valley, Sacramento's 2020 p ...
and the
Feather River The Feather River is the principal tributary of the Sacramento River, in the Sacramento Valley of Northern California. The river's main stem is about long. Its length to its most distant headwater tributary is just over . The main stem Feather ...
canyon/
Beckwourth Pass Beckwourth Pass is the lowest mountain pass in the Sierra Nevada mountain range at an elevation of . Geography Beckwourth Pass is located at the north eastern edge of Sierra Valley at Chilcoot-Vinton, California near the border between Pl ...
crossing of the Sierra Nevada Formed in 1909, the Oakland Antioch Railway was renamed the ''Oakland Antioch & Eastern Railway'' in 1911. It extended through a tunnel in the Oakland Hills, from Oakland to Walnut Creek, Concord and on to Bay Point. The current owner of the Santa Fe Railroad's assets,
BNSF Railway BNSF Railway is the largest freight railroad in the United States. One of six North American Class I railroads, BNSF has 36,000 employees, of track in 28 states, and over 8,000 locomotives. It has three Transcontinental railroad, transcontine ...
, has the terminus of its transcontinental route in
Richmond Richmond most often refers to: * Richmond, British Columbia, a city in Canada * Richmond, California, a city in the United States * Richmond, London, a town in the London Borough of Richmond upon Thames, England * Richmond, North Yorkshire, a town ...
. Originally built by the San Francisco and San Joaquin Valley Railroad in 1896, the line was purchased by the
Atchison, Topeka and Santa Fe Railway The Atchison, Topeka and Santa Fe Railway , often referred to as the Santa Fe or AT&SF, was one of the largest Class 1 railroads in the United States between 1859 and 1996. The Santa Fe was a pioneer in intermodal freight transport; at vario ...
shortly thereafter. The line leaves Richmond through industrial and residential parts of West County before striking due east through Franklin Canyon and Martinez on its way to
Stockton Stockton may refer to: Places Australia * Stockton, New South Wales * Stockton, Queensland, a locality in the Cassowary Coast Region New Zealand *Stockton, New Zealand United Kingdom * Stockton, Cheshire *Stockton, Norfolk * Stockton, Chi ...
,
Bakersfield Bakersfield is a city in and the county seat of Kern County, California, United States. The city covers about near the southern end of the San Joaquin Valley, which is located in the Central Valley region. Bakersfield's population as of the ...
, and Barstow. These railroads spurred the development of industry in the county throughout the late 19th and early 20th centuries, particularly driving development of the
Standard Oil Standard Oil Company was a Trust (business), corporate trust in the petroleum industry that existed from 1882 to 1911. The origins of the trust lay in the operations of the Standard Oil of Ohio, Standard Oil Company (Ohio), which had been founde ...
(now
Chevron Chevron (often relating to V-shaped patterns) may refer to: Science and technology * Chevron (aerospace), sawtooth patterns on some jet engines * Chevron (anatomy), a bone * '' Eulithis testata'', a moth * Chevron (geology), a fold in rock la ...
)
refinery A refinery is a production facility composed of a group of chemical engineering unit processes and unit operations refining certain materials or converting raw material into products of value. Types of refineries Different types of refineries ...
and port complex in Richmond. There were a large number of short lines in the county between the late 19th century and the early 20th century. The rights of way of a number of these railroads also served as utility rights of way, particularly for water service, and so were preserved and in the late 20th century enhanced as walking, jogging, and bicycle riding trails in the central portion of the county.


Attractions

*
Black Diamond Mines Regional Preserve The Black Diamond Mines Regional Preserve is a park located north of Mount Diablo in Contra Costa County, California under the administration of the East Bay Regional Park District (EBRPD). The district acquired the property in 1973. The pre ...
*
Blackhawk Museum The Blackhawk Museum, founded in 1988, consists of five distinct galleries in a facility in Danville, California with a significant collection of classic car, classic, rare, and unique automobiles. In addition to its gallery ''Classic Car Collecti ...
(This site also contains a
paleontological Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...
museum of the
University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a Public university, public Land-grant university, land-grant research university in Berkeley, California, United States. Founded in 1868 and named after t ...
) * John Marsh House (not open to the public) *
Eugene O'Neill National Historic Site The Eugene O'Neill National Historic Site, located in Danville, California, preserves Tao House, the Monterey Colonial hillside home of America's only Nobel Prize-winning playwright, Eugene O'Neill. History of Tao House Eugene O'Neill had won ...
*
John Muir National Historic Site The John Muir National Historic Site is located in the San Francisco Bay Area, in Martinez, Contra Costa County, California. It preserves the 14-room Italianate Victorian mansion where the naturalist and writer John Muir lived, as well as a ne ...
* Lindsay Wildlife Museum *
Don Francisco Galindo House The Don Francisco Galindo House, known locally as the Galindo House and Gardens, is a 19th-century house in Concord, California built in 1856 by Francisco Galindo and his wife, Maria Dolores Manuela (Pacheco) Galindo, daughter of Salvio Pacheco ...
*
Don Salvio Pacheco Adobe The Salvio Pacheco Adobe is a historic adobe house in Concord, California. It was built in 1835 by Salvio Pacheco, a Californio ranchero with vast lands in Contra Costa. History In 1834, Salvio Pacheco was awarded the Rancho Monte del Diablo ...
* Martinez Adobe * San Ramon Valley Museum * Borges Ranch * Richmond Museum of History *
Rosie the Riveter/World War II Home Front National Historical Park Rosie the Riveter World War II Home Front National Historical Park is a United States national historical park National Historic Site (NHS) and National Historical Park (NHP) are designations for officially recognized areas of nationally hi ...
*
Vasco Caves Regional Preserve Vasco Caves Regional Preserve is a natural and cultural protected area located on the eastern slope of Mount Diablo, on Vasco Road within eastern Contra Costa County, California. It was created to preserve wildlife habitats, California chaparral ...


Parks and recreation

*
Briones Regional Park Briones Regional Park is a regional park in the East Bay Regional Park District (EBRPD) system, located in the Briones Hills of central Contra Costa County of the San Francisco Bay Area in California. Geography The park is located in rolling h ...
* Diablo Foothills * Howe Homestead Park * Marsh Creek State Park - not open to the public *
Mount Diablo State Park Mount is often used as part of the name of specific mountains, e.g. Mount Everest. Mount or Mounts may also refer to: Places * Mount, Cornwall, a village in Warleggan parish, England * Mount, Perranzabuloe, a hamlet in Perranzabuloe parish, C ...
*
Las Trampas Regional Wilderness Las Trampas Regional Wilderness is a regional park located in Alameda and Contra Costa counties in Northern California. The nearest city is Danville, California. ''Las Trampas'' is Spanish for ''the traps'', or ''the snares''. The park belongs t ...
* Shell Ridge Open Space *
Lime Ridge Open Space Lime most commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Bo ...
* San Pablo Recreation Area ( San Pablo Dam Reservoir) * Sugarloaf Open Space * Acalanes Open Space *
Point Isabel Regional Shoreline Point Isabel Regional Shoreline in Richmond, California, is operated by East Bay Regional Park District, and is a multi-use park for joggers, windsurfers, kayakers, photographers, picnickers, and people walking dogs. It has access for pedestrian ...
in
Richmond Richmond most often refers to: * Richmond, British Columbia, a city in Canada * Richmond, California, a city in the United States * Richmond, London, a town in the London Borough of Richmond upon Thames, England * Richmond, North Yorkshire, a town ...
is the largest dog park in the country. *Adjoining or nearby these parks are lands of the
East Bay Municipal Utility District East Bay Municipal Utility District (EBMUD), colloquially referred to as "East Bay Mud", is a public utility district which provides water and sewage treatment services for an area of approximately in the eastern side of San Francisco Bay.Sectio ...
. These require special annual permits for hiking, bicycle riding and horse riding, available for a small fee. At least one member of a party traversing these areas must have such a permit.


Trails

*
Iron Horse Regional Trail The Iron Horse Regional Trail is a rail trail for pedestrians, horse riders and bicycles in the East Bay (San Francisco Bay Area), East Bay Area in California. This trail is located in inland central Alameda County, California, Alameda and ...
* California State Riding and Hiking Trail *
Contra Costa Canal Regional Trail Contra may refer to: Places * Contra, Virginia * Contra Costa Canal, an aqueduct in the U.S. state of California * Contra Costa County, California * Tenero-Contra, a municipality in the district of Locarno in the canton of Ticino in Switzerland ...
* Delta de Anza Regional Trail * Briones-Mount Diablo Regional Trail * Lafayette-Moraga Regional Trail * Marsh Creek Regional Trail *
American Discovery Trail The American Discovery Trail is a system of recreational trails and roads that collectively form a coast-to-coast hiking and biking trail across the mid-tier of the United States. Horses can also be ridden on most of this trail. The coastal tr ...

Hiking trails in Contra Costa County


Utilities

* Central Contra Costa Sanitary District * Contra Costa Water District *
East Bay Municipal Utility District East Bay Municipal Utility District (EBMUD), colloquially referred to as "East Bay Mud", is a public utility district which provides water and sewage treatment services for an area of approximately in the eastern side of San Francisco Bay.Sectio ...


Communities


Cities

*
Antioch Antioch on the Orontes (; , ) "Antioch on Daphne"; or "Antioch the Great"; ; ; ; ; ; ; . was a Hellenistic Greek city founded by Seleucus I Nicator in 300 BC. One of the most important Greek cities of the Hellenistic period, it served as ...
* Brentwood * Clayton *
Concord Concord may refer to: Meaning "agreement" * Harmony, in music * Agreement (linguistics), a change in the form of a word depending on grammatical features of other words Arts and media * ''Concord'' (video game), a defunct 2024 first-person sh ...
* El Cerrito *
Hercules Hercules (, ) is the Roman equivalent of the Greek divine hero Heracles, son of Jupiter and the mortal Alcmena. In classical mythology, Hercules is famous for his strength and for his numerous far-ranging adventures. The Romans adapted the Gr ...
* Lafayette * Martinez (county seat) * Oakley *
Orinda Orinda is a city in Contra Costa County, California, United States. The city's population as of the 2020 census is estimated at 19,514 residents. History Orinda is located within four Mexican land grants: Rancho Laguna de los Palos Colorado ...
*
Pinole Pinole, also called pinol, is roasted ground maize. The resulting powder is then used as a nutrient-dense ingredient to make different foods, such as cereals, baked goods, tortillas, and beverages. For example, it can be mixed with a combination ...
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Pittsburg Pittsburg may refer to: Places United States Cities, towns, townships and counties *Pittsburg, California * Pittsburg, Florida *Pittsburg, Kansas, Crawford County *Pittsburg, New Hampshire * Pittsburg, Oklahoma *Pittsburg, Texas *Pittsburg Coun ...
* Pleasant Hill *
Richmond Richmond most often refers to: * Richmond, British Columbia, a city in Canada * Richmond, California, a city in the United States * Richmond, London, a town in the London Borough of Richmond upon Thames, England * Richmond, North Yorkshire, a town ...
* San Pablo * San Ramon * Walnut Creek


Towns

* Danville * Moraga


Census-designated places

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Acalanes Ridge Acalanes Ridge is a census-designated place in Contra Costa County, California. Acalanes Ridge sits at an elevation of . The population was 1,285 at the 2020 Census. Acalanes Ridge was created a census-designated place for the 2010 census, and ...
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Alamo The Battle of the Alamo (February 23 – March 6, 1836) was a pivotal event and military engagement in the Texas Revolution. Following a 13-day siege, Mexican troops under President General Antonio López de Santa Anna reclaimed the Alam ...
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Alhambra Valley Alhambra Valley (, ) is a census-designated place in the Briones Hills of central Contra Costa County, California. Alhambra Valley sits at an elevation of . The 2020 United States census reported that Alhambra Valley's population was 805. The Span ...
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Bay Point Bay Point may refer to: * Bay Point (Antarctica) * Bay Point, California * Bay Point (former settlement), California * Bay Point, Monroe County, Florida * Bay Point (South Carolina), in Charleston, South Carolina's harbor; see Mitchelville * B ...
* Bayview * Bethel Island *
Blackhawk Black Hawk and Blackhawk may refer to: Animals * Common black hawk, ''Buteogallus anthracinus'' * Cuban black hawk, ''Buteogallus gundlachii'' * Great black hawk, ''Buteogallus urubitinga'' * Mangrove black hawk, ''Buteogallus (anthracinus) s ...
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Byron George Gordon Byron, 6th Baron Byron (22 January 1788 – 19 April 1824) was an English poet. He is one of the major figures of the Romantic movement, and is regarded as being among the greatest poets of the United Kingdom. Among his best-kno ...
* Camino Tassajara * Castle Hill * Clyde *
Contra Costa Centre Contra Costa Centre is an unincorporated community and census-designated place in Contra Costa County, California. Contra Costa Centre sits at an elevation of 92 feet (28 m). The 2010 United States census reported Contra Costa Centre's population ...
* Crockett * Diablo *
Discovery Bay Discovery Bay is a picturesque residential community located on Lantau Island. The 2021 census recorded a population of 19,336 residents in DB, with 55% of them being non-Chinese. DB is home to a significant community compared of expatriates ...
* East Richmond Heights * El Sobrante *
Kensington Kensington is an area of London in the Royal Borough of Kensington and Chelsea, around west of Central London. The district's commercial heart is Kensington High Street, running on an east–west axis. The north-east is taken up by Kensingt ...
* Knightsen * Montalvin Manor * Mountain View * Norris Canyon * North Gate * North Richmond * Pacheco *
Port Costa Port Costa is a small town and census-designated place (CDP) in Contra Costa County, California, located in the East Bay region of the San Francisco Bay Area. Situated on the southern shore of the Carquinez Strait, the population was 190 in 2020 ...
* Reliez Valley *
Rodeo Rodeo () is a competitive equestrian sport that arose out of the working practices of cattle herding in Spain and Mexico, expanding throughout the Americas and to other nations. It was originally based on the skills required of the working vaqu ...
* Rollingwood *
Saranap Saranap (until 1913, Dewing Park) is a residential census-designated place (CDP) within central Contra Costa County, California. Lying at an elevation of 180 feet (55 m), it is bounded on the south and east by portions of Walnut Creek (including ...
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San Miguel San Miguel, Spanish for Saint Michael, may refer to: Places Argentina *San Miguel Partido *San Miguel, Buenos Aires * San Miguel, Catamarca * San Miguel, Corrientes * San Miguel, La Rioja *San Miguel Arcángel, a Volga German colony in Adolfo Al ...
* Shell Ridge *
Tara Hills Tara Hills is a census-designated place (CDP) in Contra Costa County, California, United States. The population was 5,364 at the 2020 census. Geography According to the United States Census Bureau, the CDP has a total area of , all of it land. ...
* Vine Hill


Unincorporated communities

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Canyon A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency t ...
*Hasford Heights


Former communities

* Bayview-Montalvin * Port Chicago Ohmer was a rail station located on the Oakland, Antioch and Eastern Railroad east of Martinez, which still appeared on maps as of 1947. Though primarily just a rail station, it was sometimes referred to as a community.Purcell, Mae Fisher
History of Contra Costa County
, p. 309 (1940)


Ghost towns

* Judsonville * Nortonville * Point of Timber Landing * Somersville * Stewartville * West Hartley


Other places

* Livorna * Rossmoor - a senior development incorporated into Walnut Creek (not to be confused with the Southern California Rossmoor).


Population ranking

The population ranking of the following table is based on the 2020 census of Contra Costa County. † ''county seat''


See also

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National Register of Historic Places listings in Contra Costa County, California __NOTOC__ This is a list of the National Register of Historic Places listings in Contra Costa County, California. This is intended to be a complete list of the properties and districts on the National Register of Historic Places in Contra Costa ...
* List of museums in San Francisco Bay Area, California *
Stege, California Stege, founded in 1876, was an unincorporated community in western Contra Costa County, California, United States. The town has now been annexed and absorbed by the cities of Richmond
, former unincorporated area within the county


Notes


References


External links

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Contra Costa County Library

Contra Costa County Office of Education - ROP

Contra Costa Health Services

ContraCostaMeansBusiness.com - Contra Costa County's Business Portal

Contra Costa Countywide Youth Commission (CYC)

Contra Costa County Historical Society
{{Authority control California counties Counties in the San Francisco Bay Area 1850 establishments in California Populated places established in 1850 Majority-minority counties in California