Jefferson County 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 In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its so ...

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

. As of the 2020 census, the population was 582,910, making it the fourth-most populous county in Colorado. 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 Golden, and the most populous city is Lakewood. Jefferson County is included in the

Denver Denver ( ) is a List of municipalities in Colorado#Consolidated city and county, consolidated city and county, the List of capitals in the United States, capital and List of municipalities in Colorado, most populous city of the U.S. state of ...

Aurora An aurora ( aurorae or auroras), also commonly known as the northern lights (aurora borealis) or southern lights (aurora australis), is a natural light display in Earth's sky, predominantly observed in high-latitude regions (around the Arc ...

-Lakewood, CO Metropolitan Statistical Area. Located along the

Front Range The Front Range is a mountain range of the Southern Rocky Mountains of North America located in the central portion of the U.S. State of Colorado, and southeastern portion of the U.S. State of Wyoming. It is the first mountain range encounter ...

of the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from the northernmost part of Western Can ...

, Jefferson County is adjacent to the state capital of Denver. In 2010, the center of population of Colorado was located in Jefferson County. The county's slogan is the "Gateway to the Rocky Mountains", and it is commonly nicknamed Jeffco. The name Jeffco is incorporated in the name of the Jeffco School District, the Jeffco Business Center Metropolitan District No. 1, and several businesses located in Jefferson County. Jeffco is also incorporated in the unofficial monikers of many Jefferson County agencies. The Rocky Mountain Metropolitan Airport operated by Jefferson County was previously known as the Jeffco Airport. A major employer in Jefferson County is the large

Coors Brewing Company The Coors Brewing Company is an American brewery and beer company based in Golden, Colorado, that was founded in 1873. In 2005, Adolph Coors Company, the holding company that owned Coors Brewing, merged with Molson, Inc. to become Molson Coor ...

in Golden. Also, the state-supported

Colorado School of Mines The Colorado School of Mines (Mines) is a public research university in Golden, Colorado, United States. Founded in 1874, the school offers both undergraduate and graduate degrees in engineering, science, and mathematics, with a focus on ener ...

, a university specializing in

mining Mining is the Resource extraction, extraction of valuable geological materials and minerals from the surface of the Earth. Mining is required to obtain most materials that cannot be grown through agriculture, agricultural processes, or feasib ...

geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...

chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

, and

engineering Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...

is located in Jefferson County.

History

On August 25, 1855, the Kansas Territorial Legislature created Arapahoe County to govern the entire western portion of the

territory A territory is an area of land, sea, or space, belonging or connected to a particular country, person, or animal. In international politics, a territory is usually a geographic area which has not been granted the powers of self-government, ...

. The county was named for the Arapaho Nation of Native Americans who lived in the region. In June 1858,

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

was discovered along the

South Platte River The South Platte River is one of the two principal tributaries of the Platte River. Flowing through the U.S. states of Colorado and Nebraska, it is itself a major river of the American Midwestern United States, Midwest and the American Sou ...

in Arapahoe County (in present-day Englewood) by

William Greeneberry Russell William Greeneberry "Green" Russell (1818–1877) was an American gold prospector and miner. Early life Green Russell was born in South Carolina but moved with his family to Georgia as a small child. His father James Russell engaged in gold mini ...

and Sam Bates who had been following up the June 22, 1850, discovery of gold on Ralston Creek in today's Jefferson County by Lewis Ralston, for whom the creek was named. This discovery precipitated the Pike's Peak Gold Rush. The Doniphan Party upon arriving upon Clear Creek discovered markers left over from earlier mining in 1834 by the Estes Party, placed their own alongside and on November 29, 1858, founded the future county's first town of Arapahoe City upon the land southeast of today's West 44th Avenue and McIntyre Street (with West 44th running through the town). On June 16, 1859, its second town,

Golden, Colorado Golden is a home rule city that is the county seat of Jefferson County, Colorado, United States. The city population was 20,399 at the 2020 United States census. Golden lies along Clear Creek at the base of the Front Range of the Rocky Moun ...

, was founded in the valley to the west. Many residents of the mining region felt disconnected from the remote territorial governments of

Kansas Kansas ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named a ...

and

Nebraska Nebraska ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Ka ...

, so they voted to form their own Territory of Jefferson on October 24, 1859. The following month on November 28, 1859, the Jefferson Territorial Legislature organized 12 counties for the new territory, including Jefferson County. Jefferson County was named for the namesake of the Jefferson Territory,

Thomas Jefferson Thomas Jefferson (, 1743July 4, 1826) was an American Founding Fathers of the United States, Founding Father and the third president of the United States from 1801 to 1809. He was the primary author of the United States Declaration of Indepe ...

, the principal author of the

Declaration of Independence A declaration of independence is an assertion by a polity in a defined territory that it is independent and constitutes a state. Such places are usually declared from part or all of the territory of another state or failed state, or are breaka ...

and the nation's third

president President most commonly refers to: *President (corporate title) * President (education), a leader of a college or university *President (government title) President may also refer to: Arts and entertainment Film and television *'' Præsident ...

. Golden City was elected on January 2, 1860, as the

of Jefferson County. Robert Williamson Steele,

Governor A governor is an politician, administrative leader and head of a polity or Region#Political regions, political region, in some cases, such as governor-general, governors-general, as the head of a state's official representative. Depending on the ...

of the Provisional Government of the Territory of Jefferson from 1859 to 1861, built his home in the county at

Mount Vernon Mount Vernon is the former residence and plantation of George Washington, a Founding Father, commander of the Continental Army in the Revolutionary War, and the first president of the United States, and his wife, Martha. An American landmar ...

and later at

Apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics) A-Bomb Abomination Absorbing Man Abraxas Abyss Abyss is the name of two characters appearing in Ameri ...

. Originally Jefferson County's borders extended to the

40th parallel north Following are circles of latitude between the 35th parallel north and the 40th parallel north: 36th parallel north The 36th parallel north is a circle of latitude that is 36 degrees north of the Earth's equatorial plane. It crosses Africa, t ...

, the

(excluding the town of Highland) to the east, and to Bear Creek to the south. The Jefferson Territory never received federal sanction, but during his last week in office,

President President most commonly refers to: *President (corporate title) * President (education), a leader of a college or university *President (government title) President may also refer to: Arts and entertainment Film and television *'' Præsident ...

James Buchanan James Buchanan Jr. ( ; April 23, 1791June 1, 1868) was the 15th president of the United States, serving from 1857 to 1861. He also served as the United States Secretary of State, secretary of state from 1845 to 1849 and represented Pennsylvan ...

signed an act which organized the Territory of Colorado on February 28, 1861. That November 1, the new

Colorado General Assembly The Colorado General Assembly is the state legislature of the State of Colorado. It is a bicameral legislature consisting of the Senate and House of Representatives that was created by the 1876 state constitution. Its statutes are codified in ...

organized the 17 original counties of Colorado, including Jefferson County. The reorganized Jefferson County extended to most of its current borders and Golden continued as county seat. In 1908, the southern tip of Jefferson County was transferred to Park County, reducing Jefferson County to its present length of . Several annexations by the City & County of Denver and the 2001 consolidation of the City & County of Broomfield removed the east and extreme northeastern corner of the county, respectively.

Geography

At the 2020 United States census, the county had a total area of , of which is land and (1.3%) is water. As of April 1, 2020, the mean population center of the State of Colorado was located in Jefferson County at coordinates near the (ironically) tiny hamlet of Phillipsburg.

Adjacent counties

Jefferson County is one of the few counties in the United States to border as many as ten counties. * Boulder County – north * City and County of Broomfield – northeast * Adams County – east *

City and County of Denver Denver ( ) is a consolidated city and county, the capital and most populous city of the U.S. state of Colorado. It is located in the Western United States, in the South Platte River Valley on the western edge of the High Plains east of ...

– east * Arapahoe County – east * Douglas County – east * Teller County – south * Park County – southwest * Clear Creek County – west * Gilpin County – northwest

Major highways

Interstate 70 Interstate 70 (I-70) is a major east–west Interstate Highway in the United States that runs from Interstate 15, I-15 near Cove Fort, Utah, to Interstate 695 (Maryland), I-695 and Maryland Route 570 (MD 570) in Woodlawn, Baltimo ...

* *

U.S. Highway 6 * US 40

U.S. Highway 40 * US 285

U.S. Highway 285 * Colorado 8

State Highway 8 * Colorado 58

State Highway 58 * Colorado 72

State Highway 72 * Colorado 74

State Highway 74 * Colorado 75

State Highway 75 * Colorado 93

State Highway 93 * Colorado 121

State Highway 121 * Colorado 391

State Highway 391 * Colorado 470

State Highway 470 * Chatfield Ave * 44th Ave

Recreational areas

*Alderfer/Three Sisters Park *Apex Park *Bear Creek Lake Park * Centennial Cone Park *Clear Creek Canyon Park *Coal Creek Canyon * Crown Hill Park *Deer Creek Canyon Park * Elk Meadow Park *Evergreen Lake *Fairmount Trail *Flying J Ranch Park *Hildebrand Ranch Park * Hiwan Homestead Museum *Lair o' the Bear Park *Lewis Meadows Park *Lookout Mountain Nature Center *Matthews/Winters Park *Meyer Ranch Park *Mount Falcon Park *Mount Galbraith Park *Mount Glennon * Mount Lindo *North Table Mountain Park *Pine Valley Ranch Park *Ranson/Edwards Homestead Ranch *Reynolds Park *Sister City Park *South Table Mountain Park * South Valley Park *Standley Lake Regional Park *Van Bibber Park *Welchester Tree Grant Park *White Ranch Park *Windy Saddle Park *Urban Trails

Demographics

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 527,056 people, 206,067 households, and 140,537 families residing in the county. The

population density Population density (in agriculture: Standing stock (disambiguation), standing stock or plant density) is a measurement of population per unit land area. It is mostly applied to humans, but sometimes to other living organisms too. It is a key geog ...

was . There were 212,488 housing units at an average density of . The racial makeup of the county was : There were 206,067 households, out of which 33.40% had children under age 18 living with them, 55.10% were

married couples Marriage, also called matrimony or wedlock, is a culturally and often legally recognised union between people called spouses. It establishes rights and obligations between them, as well as between them and their children (if any), and b ...

living together, 9.10% had a female householder with no husband present, and 31.80% were non-families. 24.50% of all households were made up of individuals, of those 6.30% were someone living alone who was 65 years of age or older. The average household size was 2.52, and the average family size was 3.03 persons. In the county, the population ages were spread out: : For every 100 females there were 99.00 males. For every 100 females age 18 and over, there were 96.80 males. The median income for a household in the county was $57,339, and the median income for a family was $67,310. Males had a median income of $45,306 versus $32,372 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 $28,066. About 3.40% of families and 5.20% 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 5.80% of those under age 18, and 5.10% of those age 65 or over. According to a report in the

JAMA ''JAMA'' (''The Journal of the American Medical Association'') is a peer-reviewed medical journal published 48 times a year by the American Medical Association. It publishes original research, reviews, and editorials covering all aspects of b ...

, residents of Jefferson County had a 2014 life expectancy of 80.02 years.

Education

The sole school district serving the county is Jefferson County School District R-1. ;Private schools: *

Colorado Academy Colorado Academy (CA) is an independent nonsectarian, co-educational, college preparatory day school for students from Pre-Kindergarten through Twelfth Grade. The school's campus is located in Lakewood, Colorado, and serves approximately 1000 ...

;Higher Education: *

Colorado Christian University Colorado Christian University (CCU) is a private Christian university in Lakewood, Colorado, United States. CCU was founded by Clifton Fowler in 1914 as the Denver Bible Institute. History CCU's heritage dates back to the formation of Denver Bi ...

Red Rocks Community College Red Rocks Community College (RRCC) is a Public university, public community college with two campuses located in Lakewood, Colorado, Lakewood and Arvada, Colorado. History RRCC was established in 1969 as part of the Colorado Community Colle ...

* Rocky Mountain College of Art and Design Jefferson County Public Library is the county library system.

Government and infrastructure

*The Federal Correctional Institution, Englewood is in unincorporated Jefferson County. *The Rocky Flats Plant produced nuclear weapons in Jefferson County from 1952 until 1989. *The Jefferson County Public Library, established in 1952. *The Jefferson County Government Center, also known as the "courts and admin building". *The Denver Federal Center, the largest concentration of federal government agencies outside of

Washington, D.C. Washington, D.C., formally the District of Columbia and commonly known as Washington or D.C., is the capital city and federal district of the United States. The city is on the Potomac River, across from Virginia, and shares land borders with ...

, is located in Lakewood.

Government

The Board of County Commissioners operates as the governing body of the county. Established in 1861, the board consists of three commissioners who are elected

at-large At large (''before a noun'': at-large) is a description for members of a governing body who are elected or appointed to represent a whole membership or population (notably a city, county, state, province, nation, club or association), rather tha ...

to four-year terms. The board sets policies that guide county programs and operations which serves residents and businesses. There are several elected officials that oversee a department or aspect of county operations. Jefferson County lies within the 1st Judicial District which is represented by District Attorney Alexis King.

Sheriff's office

The Jefferson County Sheriff is an oldest elective office in Jefferson County (along with Clerk and Recorder, Assessor and Treasurer) and among the first popularly elected offices in Colorado, established in 1859 with the first Sheriff, Walter Pollard, elected on January 2, 1860. Its office holders over the course of over 150 years have included some of the most noted law enforcement officers in Colorado history. The Jefferson County Sheriff's Office responded to the 1999

Columbine High School massacre A school shooting and attempted bombing occurred on April 20, 1999, at Columbine High School in Columbine, Colorado, United States. The perpetrators, twelfth-grade students Eric Harris and Dylan Klebold, murdered 13 students and one teach ...

, and investigated it together with the F.B.I. The Sheriff's Office received backlash after it was revealed the agency had the perpetrators

Eric Harris and Dylan Klebold Eric David Harris (April 9, 1981 – April 20, 1999) and Dylan Bennet Klebold ( ; September 11, 1981 – April 20, 1999) were American high school seniors and mass murderers who perpetrated the Columbine High School massacre at Columbine ...

in and out of custody prior to the shooting. After the shooting Sue Klebold sued the Sheriff's office for failing to prevent their son from carrying out the Columbine High shootings. According to a "notice of intent to sue" filed by Susan and Thomas Klebold, county officials were "reckless, willful and wanton" in the way they handled a 1998 police report about Eric Harris' Internet ravings. This lawsuit was dismissed along with several others pertaining to the shooting. The current county sheriff is Regina "Reggie" Marinelli. She was elected in 2022 and became the first woman to do so in county history and became the first Democrat to hold the office in nearly a century. She previously worked in the county Sheriff's Office for over 30 years.

Politics

Jefferson County was a Republican stronghold for most of the 20th century, voting Republican in all but one presidential election between 1940 and 2004. However, it has voted Democratic in every presidential election since 2008, consistent with the general trend in the Denver metropolitan area. In

2024 The year saw the list of ongoing armed conflicts, continuation of major armed conflicts, including the Russian invasion of Ukraine, the Myanmar civil war (2021–present), Myanmar civil war, the Sudanese civil war (2023–present), Sudane ...

Kamala Harris Kamala Devi Harris ( ; born October 20, 1964) is an American politician and attorney who served as the 49th vice president of the United States from 2021 to 2025 under President Joe Biden. She is the first female, first African American, and ...

won the largest percentage for a Democratic presidential candidate since 1916.

Recreation

State parks

* Chatfield State Park * Golden Gate Canyon State Park *

Staunton State Park Staunton State Park is a Colorado state park in Park and Jefferson counties, located west of Conifer, Colorado. The park, which opened on May 18, 2013, includes dramatic rock outcroppings, several streams and a waterfall. On December 4, 201 ...

National forests and wilderness

* Pike National Forest *

Roosevelt National Forest The Roosevelt National Forest is a National Forest located in north central Colorado. It is contiguous with the Colorado State Forest as well as the Arapaho National Forest and the Routt National Forest. The forest is administered jointly w ...

* Lost Creek Wilderness

National wildlife refuges

* Rocky Flats National Wildlife Refuge * Two Ponds National Wildlife Refuge

Historic trail

* South Platte Trail

Recreational trails

* American Discovery Trail * Apex National Recreation Trail * Big Dry Creek National Recreation Trail * Colorado Trail * Platte River Greenway National Recreation Trail * Two Ponds National Recreation Trail

Scenic byway

* Lariat Loop Scenic and Historic Byway

Golf course

* Hiwan Golf Club * Indian Tree Golf Club

Communities

Cities

* Arvada (part) * Edgewater * Golden * Lakewood * Littleton (part) *

Westminster Westminster is the main settlement of the City of Westminster in Central London, Central London, England. It extends from the River Thames to Oxford Street and has many famous landmarks, including the Palace of Westminster, Buckingham Palace, ...

(part) * Wheat Ridge

Towns

* Bow Mar (part) * Lakeside *

Morrison Morrison may refer to: People * Morrison (surname), people with the Scottish surname Morrison * Morrison Heady (1829–1915), American poet * Morrison Mann MacBride (1877–1938), Canadian merchant Places in the United States * Morrison, Colorad ...

* Mountain View * Superior (part)

Census-designated places

* Applewood * Aspen Park * Brook Forest * Coal Creek (part) * Columbine * Dakota Ridge * East Pleasant View *

Evergreen In botany, an evergreen is a plant which has Leaf, foliage that remains green and functional throughout the year. This contrasts with deciduous plants, which lose their foliage completely during the winter or dry season. Consisting of many diffe ...

* Fairmount * Genesee * Idledale * Indian Hills * Ken Caryl * Kittredge * West Pleasant View

Unincorporated communities

* Buffalo Creek *

Conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...

* Foxton *

Pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...

* Pine Junction *

Plastic Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...

References

External links

Jefferson County Government websiteColorado Historical Society
{{coord, 39.59, -105.25, display=title, type:adm2nd_region:US-CO_source:UScensus1990 Colorado counties 1861 establishments in Colorado Territory Denver metropolitan area Populated places established in 1861