The Santa Susana Mountains are a transverse range of mountains in

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 ...

, north of the city of

Los Angeles Los Angeles, often referred to by its initials L.A., is the List of municipalities in California, most populous city in the U.S. state of California, and the commercial, Financial District, Los Angeles, financial, and Culture of Los Angeles, ...

, in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

. The range runs east-west, separating the San Fernando and Simi valleys on its south from the Santa Clara River Valley to the north and the Santa Clarita Valley to the northeast. The Oxnard Plain is to the west of the Santa Susana Mountains.

Description

Geography

The Newhall Pass separates the Santa Susana Mountains from the

San Gabriel Mountains The San Gabriel Mountains () are a mountain range located in Los Angeles and San Bernardino counties, California, United States. The mountain range is part of the Transverse Ranges and lies between the Los Angeles Basin and the Mojave Desert ...

to the east. Newhall Pass is the major north-south connection between the San Fernando and Santa Clarita valleys, and

Interstate 5 Interstate 5 (I-5) is the main north–south Interstate Highway System, Interstate Highway on the West Coast of the United States, running largely parallel to the Pacific coast of the contiguous U.S. from Mexico to Canada. It travels thro ...

and a railroad line share Newhall Pass. The Santa Susana Pass (containing SR 118) connects the Simi and San Fernando valleys, and separates the Santa Susana Mountains from the

Simi Hills The Simi Hills are a low rocky mountain range of the Transverse Ranges in eastern Ventura County, California, Ventura County and western Los Angeles County, California, Los Angeles County, of Southern California, United States. The range runs ma ...

to the south. Santa Susana Pass State Historic Park is located in the Simi Hills, just south of the Santa Susana Pass, at the northwestern edge of the San Fernando Valley. The Santa Susana Mountains are not as steep or high as the San Gabriel Mountains. The western half of the range lies in

Ventura County Ventura County () is a county located in the southern part of the U.S. state of California. As of the 2020 census, the population was 843,843. The largest city is Oxnard, and the county seat is the city of Ventura. Ventura County comprises ...

, and the eastern half lies in

Los Angeles County Los Angeles County, officially the County of Los Angeles and sometimes abbreviated as LA County, is the most populous county in the United States, with 9,663,345 residents estimated in 2023. Its population is greater than that of 40 individua ...

. The southeastern slopes of the Santa Susana Mountains are part of the City of

, and housing subdivisions, including Porter Ranch, have been built on the lower slopes of the range. The city of Simi Valley lies to the southwest. North of the range is the fast-growing city of Santa Clarita, and several large subdivisions in unincorporated Los Angeles County, including Lyons Ranch and Newhall Ranch, have been approved for development. The Sunshine Canyon Landfill is at the mountains' eastern end, and several canyons in the northwest corner of the range have been proposed for more

landfill A landfill is a site for the disposal of waste materials. It is the oldest and most common form of waste disposal, although the systematic burial of waste with daily, intermediate and final covers only began in the 1940s. In the past, waste was ...

s. The Santa Susana Mountains are paralleled by State Route 118 to the south and State Route 126 to the north.

Climate

The mountains have a mild climate, with warm, dry summers and cool, wet winters (Mediterranean climate type). Snow falls in winter in some higher areas, such as Oat Mountain, but melts quickly. Annual precipitation totals vary between 18 and 25 inches, depending on exposure to the rain-bearing winds. Most of the rain falls between November and March. Because of the summer drought, wildfires sometimes occur in summer and fall before the rains start, especially during hot, dry "Santa Ana" wind events (mostly between late September to mid November).

Peaks

The highest peaks in the range are Oat Mountain (1,142 m; 3,747 feet), Mission Point (845 m; 2,771 feet), Rocky Peak (827 m; 2,714 feet), and Sand Rock Peak (765 m; 2,511 feet). The summit of Rocky Peak lies directly atop the line separating Ventura and

counties and is indicated by a battered marker embedded into the

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 ...

boulder summit.

History

The first discovery of oil in California was in Pico Canyon, on the north side of the mountains, The California Star Oil Works, later Chevron, succeeded with '' Pico Well No. 4''. It became famous not only as the first well in California, but also as the longest-producing well in the world, having been capped in September, 1990 after 114 years. Well No. 4 has the distinction of being the first site in Los Angeles County to be listed on the

National Register of Historic Places The National Register of Historic Places (NRHP) is the Federal government of the United States, United States federal government's official United States National Register of Historic Places listings, list of sites, buildings, structures, Hist ...

, in 1966. The surrounding town, Mentryville, is maintained as the oil "ghost town" Mentryville Historical Park, withi
Pico Canyon Park
Many active oil and gas fields remain in the area, with some of the larger operators including Vintage Production, Freeport McMoRan, and the Southern California Gas Company. The largest of SoCalGas's four underground storage natural gas facilities is within the Aliso Canyon Oil Field north of Porter Ranch. The mountains are within the acquisition area for the Santa Monica Mountains Conservancy, which operates several parks, includin
Santa Clarita Woodlands Park
Rocky Peak Park
Joughin Open Space PreserveHappy Camp Canyon Regional Park
and othe
Santa Susana parks
in the Santa Susana Mountains through the Mountains Recreation and Conservation Authority. The City of Los Angeles maintains O'Melveny Park at the eastern end of the mountains. Note: the

Santa Susana Field Laboratory The Santa Susana Field Laboratory (SSFL), formerly known as Rocketdyne, is a complex of industrial research and development facilities located on a portion of Southern California in an unincorporated area of Ventura County in the Simi Hills betw ...

, once operated by and still owned by

Rocketdyne Rocketdyne is an American rocket engine design and production company headquartered in Canoga Park, California, Canoga Park, in the western San Fernando Valley of suburban Los Angeles, California, Los Angeles, in southern California. Rocketdyne ...

until toxics are cleaned up, is actually in the

, which are adjacent to the south of the Santa Susana Mountains.

Plants and animals

Flora

The south-facing slopes are mostly covered in

Chaparral Chaparral ( ) is a shrubland plant plant community, community found primarily in California, southern Oregon, and northern Baja California. It is shaped by a Mediterranean climate (mild wet winters and hot dry summers) and infrequent, high-intens ...

shrubland Shrubland, scrubland, scrub, brush, or bush is a plant community characterized by vegetation dominance (ecology), dominated by shrubs, often also including grasses, herbaceous plant, herbs, and geophytes. Shrubland may either occur naturally o ...

grassland A grassland is an area where the vegetation is dominance (ecology), dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes such as clover, and other Herbaceo ...

s, and

oak An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...

savanna. The north-facing slopes are home to magnificent oak woodlands and conifer (fir) woodlands, some of which have been protected in the Santa Clarita Woodlands Park and other large open space preserves. The mountains are part of the

California chaparral and woodlands The California chaparral and woodlands is a terrestrial ecoregion of southwestern Oregon, northern, central, and southern California (United States) and northwestern Baja California (Mexico), located on the west coast of North America. It is a ...

ecoregion An ecoregion (ecological region) is an ecological and geographic area that exists on multiple different levels, defined by type, quality, and quantity of environmental resources. Ecoregions cover relatively large areas of land or water, and c ...

. The

s, (''Quercus spp.''), include the

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 ...

coast live oak (''Quercus agrifolia''), the

deciduous In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...

valley oak (''Quercus lobata''), and the coastal scrub oak (''Quercus dumosa'') all can be found in the area. Spring

wildflower A wildflower (or wild flower) is a flower that grows in the wild, rather than being intentionally seeded or planted. The term implies that the plant is neither a hybrid nor a selected cultivar that is any different from the native plant, eve ...

s include the redbush monkey flower, Mariposa lily, and canyon sunflower. Poison oak is also an important member of the native plant habitat community. Various ferns are found in moister and tree-shaded areas.

Fauna

Many bird species thrive in the Santa Susana Mountains. Perhaps the most common raptors observed soaring over the brushy, boulder-strewn landscape are turkey vultures,

red-tailed hawk The red-tailed hawk (''Buteo jamaicensis'') is a bird of prey that breeds throughout most of North America, from the interior of Alaska and northern Canada to as far south as Panama and the West Indies. It is one of the most common members of ...

s, and American kestrels. In oak woodlands it is not uncommon to see red-shouldered hawks flying from limb to limb. Through the cover of dense, trailside chaparral you might glimpse the California towhee or the colorful spotted towhee, birds who often make their presence known by rustling up leaf litter on the ground. California quail, greater roadrunner, and

common raven The common raven or northern raven (''Corvus corax'') is a large all-black passerine bird. It is the most widely distributed of all Corvidae, corvids, found across the Northern Hemisphere. There are 11 accepted subspecies with little variatio ...

are also residents of the range. The eerie and enchanting call of the common poorwill can often be heard after dark while quick eyes might observe the silent flight of

great horned owl The great horned owl (''Bubo virginianus''), also known as the tiger owl (originally derived from early naturalists' description as the "winged tiger" or "tiger of the air") or the hoot owl, is a large owl native to the Americas. It is an extreme ...

s and phantom-like

barn owl The barn owls, owls in the genus '' Tyto'', are the most widely distributed genus of owls in the world. They are medium-sized owls with large heads and characteristic heart-shaped faces. They have long, strong legs with powerful talons. The ter ...

s. A handful of fascinating amphibians live in the area. Streams and creeks support populations of Pacific tree frog, the small amphibian whose signature chorus adds an aura of mystery and inexplicable beauty to the surrounding land. Western toads often make their appearance at nightfall, emerging from burrows in search of water and insects, while California slender salamanders are often found under the cool leaf litter and canopy of oak woodlands. Many reptiles thrive in the Santa Susana range. Lizards that are likely to be observed on any given day include the common western fence lizard and the equally abundant side-blotched lizard. Somewhat less frequently observed but still present are the southern alligator lizard, western skink, whiptail, and the seemingly rare coast horned lizard. Southern Pacific rattlesnakes and gopher snakes are perhaps the most commonly observed snakes, but a lucky hiker might also encounter other species including the striped racer, California kingsnake, and ring-necked snake. Mammals that may be regularly observed in the mountains include smaller animals such as the California ground squirrel and brush rabbit. Small mammals that are less often seen include the dusky-footed woodrat and the agile kangaroo rat. As for larger mammals, the well-trained eye might spot California mule deer or a

coyote The coyote (''Canis latrans''), also known as the American jackal, prairie wolf, or brush wolf, is a species of canis, canine native to North America. It is smaller than its close relative, the Wolf, gray wolf, and slightly smaller than the c ...

. Larger mammals that are considerably more secretive and therefore less often encountered include the

gray fox The gray fox (''Urocyon cinereoargenteus''), or grey fox, is an omnivorous mammal of the family Canidae, widespread throughout North America and Central America. This species and its only congener (biology), congener, the diminutive island fox ...

bobcat The bobcat (''Lynx rufus''), also known as the wildcat, bay lynx, or red lynx, is one of the four extant species within the medium-sized wild cat genus '' Lynx''. Native to North America, it ranges from southern Canada through most of the c ...

, ring-tailed cat, American badger, and the

mountain lion The cougar (''Puma concolor'') (, ''Help:Pronunciation respelling key, KOO-gər''), also called puma, mountain lion, catamount and panther is a large small cat native to the Americas. It inhabits North America, North, Central America, Cent ...

. A population of

American black bear The American black bear (''Ursus americanus''), or simply black bear, is a species of medium-sized bear which is Endemism, endemic to North America. It is the continent's smallest and most widely distributed bear species. It is an omnivore, with ...

s occupy various niches in the backcountry; showing up in communities below the mountains every few years. BB-12, a black bear tagged and tracked in the Santa Monica Mountains, is believed to have originated in the Santa Susana Mountains. The mountains are part of the Southern California coastal

wildlife corridor A wildlife corridor, also known as a habitat corridor, or green corridor, is a designated area habitat (ecology), that connects wildlife populations that have been separated by human activities or structures, such as development, roads, or land ...

the connects Los Padres National Forest with the Santa Monica Mountains.

Rim of the Valley Trail

The Rim of the Valley Trail is a plan in progress for connecting the parkland and recreational areas of the San Fernando, Simi, and La Crescenta Valleys via the Santa Susana Mountains. Rocky Peak Park and O'Melveny Park have trail sections already.

References

External links

SMMC: Parks in the Santa Susana Mountains
- ''with park links, by Santa Monica Mountains Conservancy.''
Santa Susana Mountain Park AssociationOfficial Santa Susana Pass State Park websiteRim of the Valley TrailNPS: Rim of the Valley Corridor Study
- ''

National Park Service The National Park Service (NPS) is an List of federal agencies in the United States, agency of the Federal government of the United States, United States federal government, within the US Department of the Interior. The service manages all List ...

project'' {{Santa Clara River Transverse Ranges Mountain ranges of Los Angeles County, California Mountain ranges of Ventura County, California Geography of the San Fernando Valley Geography of Simi Valley, California Chatsworth, Los Angeles Granada Hills, Los Angeles Moorpark, California Porter Ranch, Los Angeles Mountain ranges of Southern California