Simi Hills

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Simi Hills
Old Stagecoach Trail Santa Susana3.png
Sandstone rock formations of the Simi Hills range.
Highest point
PeakSimi Peak
Elevation 2,139 ft (652 m)
Relief map of California.png
Red triangle with thick white border.svg
location of Simi Hills in California [1]
CountryUnited States
Districts Ventura County and Los Angeles
Range coordinates 34°13′28.015″N118°43′0.326″W / 34.22444861°N 118.71675722°W / 34.22444861; -118.71675722 Coordinates: 34°13′28.015″N118°43′0.326″W / 34.22444861°N 118.71675722°W / 34.22444861; -118.71675722
Topo map USGS  Calabasas

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



The Simi Hills are aligned east-west and run for 26 miles (42 km), and average around 7 mi (11 km) in north-south width. The Simi Hills are part of the central Transverse Ranges System. They lie almost entirely within southeastern Ventura County, with some southern and eastern foothills within western Los Angeles County.

The Simi Hills are on the western edge of the San Fernando Valley. The Simi Valley lies to the north, and the Conejo Valley lies to the southwest. The San Fernando Valley communities of Chatsworth, West Hills, and Woodland Hills are in the eastern hills and adjacent valley floor in Los Angeles city and county. The cities of Agoura Hills and Westlake Village are also located in Los Angeles County, generally southwest of the Simi Hills. The cities of Thousand Oaks (to the west) and Simi Valley city (to the north) are in the hills and adjacent valleys within Ventura County.

The two nearby mountain ranges are: the higher Santa Susana Mountains adjacent on the northeast across Santa Susana Pass; and the Santa Monica Mountains running nearby along the south.


The hills provide the complete or partial watersheds for several year-round creeks and numerous seasonal streams. They include Las Virgenes Creek (tributary of Malibu Creek), Moore's Canyon Creek, Bell Creek, Dayton Creek, Woolsey Canyon Creek, Brandeis Creek, Runkle Canyon Creek, Arroyo Simi, Palo Comado Creek, Cheeseboro Creek, and Arroyo Calabasas (northern fork). Bell Creek and Arroyo Calabasas are the headwaters of the Los Angeles River, by name its beginning with their confluence in nearby Canoga Park. 90% of the Santa Susana Field Lab property drains into the Los Angeles River via tributaries.


Peaks in this region include Simi Peak, 2,403 ft (732 m), [2] Chatsworth Peak, 2,314 ft (700 m), [3] and Escorpión Peak (aka: Castle Peak), 1,475 ft (450 m).

View of Simi Hills looking south from Oakbrook Regional Park, with the Santa Monica Mountains in the distance Lang Ranch Oakbrook North Ranch Thousand Oaks May 2019 panorama 5.jpg
View of Simi Hills looking south from Oakbrook Regional Park, with the Santa Monica Mountains in the distance
Panoramic view of the Simi Hills looking north from the Santa Monica Mountains Simi Hills.jpg
Panoramic view of the Simi Hills looking north from the Santa Monica Mountains


Because of its low elevation, the Simi Hills typically experience rainy, mild winters. Snow is rare in the Simi Hills, even in the highest areas. Summers are warm and dry and wildfires do occur here. Cool winds from the Pacific Ocean come from the Oxnard Plain and blow into the inland areas through the Santa Clara River Valley and the Conejo Valley, though some low hills, such as Conejo Mountain, block these winds from the Conejo Valley. The Simi Hills further block these winds, which bring cool weather in both summer and winter from the San Fernando Valley.

Flora and fauna


The southern lower hills are mostly covered in grasslands and oak savanna. The northern rocky hills area is primarily chaparral shrubland and oak woodlands. The Simi Hills are part of the California chaparral and woodlands ecoregion. The oaks (Quercus spp.) include: the evergreen coastal live oak ( Quercus agrifolia ), the deciduous valley oak ( Quercus lobata ), and the scrub oak ( Quercus dumosa ). Riparian zone plants include California sycamores (Platanus racemosa) and arroyo willows (Salix lasiolepis). Spring wildflowers include the redbush monkey flower (Mimulus aurantiacus), Plummer's mariposa lily (Calochortus plummerae), and canyon sunflower (Encelia californica). poison oak (Toxicodendron diversilobum) is also an important member of the native plant habitat community here.


The Simi Hills is the principal, and much wider, of only two terrestrial wildlife corridors linking the coastal Santa Monica Mountains with the inland Santa Susana Mountains, Topatopa Mountains, and San Gabriel Mountains, all of the transverse ranges fauna community. The Simi Hills are the most critical wildlife corridor linkage for the Santa Monica Mountains to these and other Transverse Ranges further east.

The Simi's undeveloped native habitat provides routes that protect larger land wildlife of the Santa Monicas from genetic isolation. [4] [5] Large sections of the Simi Hills are protected by parks and open space preserves. The Santa Susana Field Laboratory property, a crucial wildlife corridor to the Santa Susanas, has been proposed for public open space parkland after the closed site's cleanup completion.

Human history

The Simi Hills were inhabited for over 8,000 years by Paleo-indians and Chumash-Venturaño Native Americans for settlements and hunting grounds. [6] [7] The Chumash had the established village of Hu'wam in Cañon del Escorpión (Bell Canyon). It was a multicultural 'crossroads' destination, where Chumash, Tongva, and Tataviam peoples traded and lived beside Bell Creek below Escorpión Peak, at the present day Bell Canyon Park. [8] [9] This peak in the Simi Hills (aka: Castle Peak) is one of nine alignment points in Chumash territory and is essential to maintaining the balance of the natural world. [10] Upstream were healing springs and are rock outcrop 'grinding stones.' The Burro Flats Painted Cave, an example of the Rock art of the Chumash people, is nearby.[ citation needed ]

The Juan Bautista de Anza expedition passed through the area in 1769, being the first European sighting of the Simi Hills. The U.S. National Park Service administers the Juan Bautista de Anza National Historic Trail which enters at Moore Canyon in El Escorpión Park and crosses across the southern Hills through Upper Las Virgenes Canyon Open Space Preserve and Cheeseboro/Palo Comado Canyon Park to the Conejo Valley. [11] In 1845 the land grant for Rancho El Escorpión, beside the Peak and named for it, was issued to one Chumash and two Tongva people and a rare instance of Native Americans being grantees, by Mexican Governor Pío Pico. The Rancho El Conejo was to the west, and included that end of the Simi Hills.[ citation needed ]

In the first half of the 20th century, there were four large movie ranches in the Simi Hills for filming motion pictures on location. The gated community of Bell Canyon began development of geographic Bell Canyon in the 1968. To the north of U.S. 101, east of Thousand Oaks, and west of Simi Valley the early 1960s suburban expansion of metropolitan Los Angeles brought the development of small to significantly sized parcels of land in the Simi Hills. Hillside subdivisions regraded natural contours into terraced lots, changing the Hills viewshed, drainage patterns, and habitats in those areas. The extensive planned new community projects at Jordan Ranch and Ahmanson Ranch were eventually stopped by local citizens and the Santa Monica Mountains Conservancy keeping extensive Hills acreage natural in open space parks.[ citation needed ]

The Simi Hills were home of the Rocketdyne Santa Susana Field Laboratory (SSFL) for open-air testing of rocket engines from 1947 to 1990, and the site of experimental nuclear reactor experiments with four nuclear accidents between 1959 and 1969; these projects and accidents were declassified in 1989. The first accident, in 1959, was the most serious with a full meltdown. The extent of the accident is unknown due to instrument limitations, other than it is released extensive radiation. More radiation was released in the 1959 event than in the Three Mile Island accident 20 years later. [12] The groundwater under portions of the Simi Hills, contaminated with toxins and radionuclides that were also historically used at SSFL, has been and are a key concern in new development decisions and the SSFL property's future limited to parkland use after an impending cleanup, initiating preservation of more open space in the range. [13]

The NPS Rim of the Valley Trail Corridor is in the planning stages and includes the Simi Hills open space parklands and proposed new areas. [14] [15] [16] [17]


Nearby ranges

See also

Related Research Articles

Santa Monica Mountains Mountain range in California, United States

The Santa Monica Mountains is a coastal mountain range in Southern California, next to the Pacific Ocean. It is part of the Transverse Ranges. Because of its proximity to densely populated regions, it is one of the most visited natural areas in California. Santa Monica Mountains National Recreation Area is located in this mountain range.

The Santa Monica Mountains Conservancy is an agency of the state of California in the United States founded in 1980 and dedicated to the acquisition of land for preservation as open space, for wildlife and California native plants habitat Nature Preserves, and for public recreation activities.

Santa Susana Mountains

The Santa Susana Mountains are a transverse range of mountains in Southern California, north of the city of Los Angeles, in the United States. The range runs east-west, separating the San Fernando Valley and Simi Valley 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.

West Hills, Los Angeles Neighborhood of Los Angeles in California, United States

West Hills is a residential and commercial neighborhood in the western San Fernando Valley region of the City of Los Angeles, California. The percentage of residents aged 35 and older is among the highest in Los Angeles County.

Santa Susana Pass

The Santa Susana Pass, originally Simi Pass, is a low mountain pass in the Simi Hills of Southern California, connecting the San Fernando Valley and Los Angeles neighborhood of Chatsworth, to the city of Simi Valley and eponymous valley.

El Escorpión Park

El Escorpión Park is a three-acre park located in the Simi Hills of the western San Fernando Valley, in the West Hills district of Los Angeles, California. The park contains the geographic landmark known as Escorpión Peak or Castle Peak, a 1,475-foot-tall rocky peak seen from most parts of the park and the surrounding community.

Rocky Peak Mountain in southern California, United States

Rocky Peak, located in Rocky Peak Park, is the fourth-highest point in the Santa Susana Mountains, and overlooks the San Fernando Valley and Chatsworth, the Simi Hills, and the Simi Valley in Southern California. The peak, which is 2,715 feet (828 m) in elevation, sits on the Los Angeles County–Ventura County line.

Upper Las Virgenes Canyon Open Space Preserve

The Upper Las Virgenes Canyon Open Space Preserve is a large open space nature preserve owned and operated by the Santa Monica Mountains Conservancy spanning nearly 3,000 acres (1,200 ha) in the Simi Hills of western Los Angeles County and eastern Ventura County.

Santa Monica Mountains National Recreation Area protected area in Southern California, USA

The Santa Monica Mountains National Recreation Area is a United States national recreation area containing many individual parks and open space preserves, located primarily in the Santa Monica Mountains of Southern California. The SMMNRA is in the greater Los Angeles region, with two thirds of the parklands in northwest Los Angeles County, and the remaining third, including a Simi Hills extension, in southeastern Ventura County.

Bell Canyon, California Place in California, United States

Bell Canyon is an unincorporated community in eastern Ventura County, California, United States. Bell Canyon is a gated community in the Simi Hills with the main access through the Los Angeles community of West Hills and the western San Fernando Valley. Bell Canyon sits at an elevation of 1,368 feet (417 m). The 2010 United States census reported Bell Canyon's population was 2,049. For statistical purposes, the United States Census Bureau has defined Bell Canyon as a census-designated place (CDP). The census definition of the area may not precisely correspond to local understanding of the area with the same name. According to a 2016 study, Bell Canyon is the seventh wealthiest community in the state of California with an annual median income of $230,000. However, incomes in this area are commonly upwards of millions of dollars a year.

Simi Peak

Simi Peak is the highest peak in the Simi Hills of Southern California, at 2,405 feet (733 m).

Bell Canyon Park is a large open-space regional park located in the Simi Hills at the western end of the San Fernando Valley in West Hills, Los Angeles and Bell Canyon, California. Bell Creek, a primary tributary to the Los Angeles River, flows through the park with riparian zone vegetation along its natural banks. The geographic landmark Escorpión Peak is high above it to the south in adjacent El Escorpión Park.

Santa Susana Pass State Historic Park

Santa Susana Pass State Historic Park is a California State Park of approximately 680 acres (2.8 km2) located on the boundary between Ventura and Los Angeles counties, between the communities of Chatsworth and Simi Valley. Geologically, the park is located where the Simi Hills meet the Santa Susana Mountains. Here in the western part of the Transverse Ranges, the land is dominated by high, narrow ridges and deep canyons covered with an abundant variety of plant life. The park offers panoramic views of the rugged natural landscape as a striking contrast to the developed communities nearby. The park is also rich in archaeological, historical, and cultural significance.

Simi Valley, California City in California, United States

The city of Simi Valley, in the eponymous valley, is in the southeast corner of Ventura County, California, United States, 40 miles (65 km) from downtown Los Angeles, making it part of the Greater Los Angeles Area. The city sits next to Thousand Oaks, Moorpark, and Chatsworth. The city's 2019 population has been estimated at 125,613, up from 124,243 in 2010. The city of Simi Valley is surrounded by the Santa Susana Mountain range and the Simi Hills, west of the San Fernando Valley, and northeast of the Conejo Valley. It grew as a commuter bedroom community for the cities in the Los Angeles area and the San Fernando Valley when a freeway was built over the Santa Susana Pass.

Bell Creek (Southern California)

Bell Creek is a 10-mile-long (16 km) tributary of the Los Angeles River, in the Simi Hills of Ventura County and the San Fernando Valley of Los Angeles County and City, in Southern California.

China Flat is a plateau in the north−central Simi Hills, in Ventura County, Southern California.

Sage Ranch Park

Sage Ranch Park is a 625-acre park (253 ha) and wildlife corridor located at a 2,000 feet (610 m) height in the northwestern Simi Hills on the northwestern plateau of the Simi Valley, bordering Los Angeles County and its San Fernando Valley. The campground area used to be a cattle ranch and later a filmset for Western movies. Sage Ranch Park is today an intermountain wildlife corridor, which links the Simi Hills with the Santa Susana- and Santa Monica Mountains. The mountainous park is mostly known for its unique sandstone rock formations, maybe particularly on its western side where the Sandstone Ridge and Turtle Rock are situated. On its northern side, there are great panoramic rural and metropolitan views of the Simi Valley, as well as surrounding Simi Hills, Santa Susana Mountains and beyond. It is home to numerous sandstone formations, caves, outcroppings, tilted rock formations, several hiking trails, a camping ground, as well as native flora and wildlife. The area is lined with coastal sage scrub and other flora includes chaparral, bush lupine, California poppy, sunflowers, Cream Cups, bracken, sword fern, prickly pear cactus, eucalyptus trees, oak woodland of ceanothus, coffee berry, California buckwheat, sycamore, Walnut Tree, ferns, orange- and avocado trees. It is a critical cross-mountain wildlife corridor and is home to fauna such as mountain lions, bobcats, eagles, vultures, owls, rattle snakes, coyotes, hawks, grey fox, king snakes, and more. Bordering Sage Ranch to the south is the Rocketdyne Santa Susana Field Laboratory, in which the nearby Burro Flats Painted Cave is located.

Tapo Canyon

Tapo Canyon is a series of canyons and a wildlife corridor in the western Santa Susana Mountains, north of Simi Valley in Ventura County, Southern California.

Bridle Path is a community in the southwestern area of the City of Simi Valley, in Ventura County, Southern California.

Arroyo Conejo Creek in the Conejo Valley, California

Arroyo Conejo is the longest creek in the Conejo Valley, sprawling over the cities of Thousand Oaks and Camarillo, and the communities of Newbury Park, Casa Conejo and Santa Rosa Valley. Arroyo Conejo is the primary drainage for the City of Thousand Oaks. Its watershed covers 57 square miles (150 km2) of which 43 square miles (110 km2) are in the Conejo Valley and 14 square miles (36 km2) in the Santa Rosa Valley.


  1. "Simi Hills". Geographic Names Information System . United States Geological Survey . Retrieved 2009-05-03.
  2. "Simi Peak". Geographic Names Information System . United States Geological Survey . Retrieved 2009-05-03.
  3. "Chatsworth Peak". Geographic Names Information System . United States Geological Survey . Retrieved 2009-05-03.
  4. Myers, Amanda Lee (June 19, 2018). "4 new mountain lion kittens found in California mountains". The Associated Press . Retrieved 21 June 2018.
  5. Roth, Annie (June 21, 2018). "Den of Mountain Lion Kittens Found in Unlikely Place". National Geographic . Retrieved 21 June 2018.
  6. USA Today article USA Today Accessed 2/22/2008
  7. "Mercury News article". Retrieved 9 April 2018.
  8. "Archived copy" (PDF). Archived from the original (PDF) on 2010-03-14. Retrieved 2010-03-23.CS1 maint: archived copy as title (link) SSPSHP Ethnohistory Accessed 2/28/2010
  9. " "Archived copy". Archived from the original on 2009-03-13. Retrieved 2010-03-24.CS1 maint: archived copy as title (link) Ahmanson Ranch Becomes Private Preserve," [Wishtoyo Foundation website. Accessed 10/23/2007
  10. Wishtoyo on Ahmanson Ranch accessed 10-23-2007 Archived 2009-03-13 at the Wayback Machine
  11. National Park Service: official Juan Bautista de Anza National Historic Trail website. accessed 4/06/2010
  12. State DTSC-SSFL_Area IV Nuclear Research section. accessed 4/06/2010
  13. State DTSC-SSFL Groundwater Interactive Database. accessed 4/06/2010
  14. access date: 6/6/2010
  15.,0,1520788.story access date: 6/6/2010
  16. access date: 6/6/2010
  17. Kamal, Sameea (March 4, 2015). "Three lawmakers urge Park Service action on Rim of the Valley study". Los Angeles Times.
  18. Bell Canyon Park. accessed 11/22/2009.
  19. Cheeseboro/Palo Comado Canyon Park. accessed 6/6/2010.
  20. Cheeseboro Park. accessed 11/22/2009.
  21. Cheeseboro/Palo Comado Canyon Park
  22. El Escorpión Park. accessed 11/22/2009.
  23. Peak. accessed 4/04/2010
  24. www.lamountains. Rocky Peak Park. access date: 6/6/2010
  25. SMMC-Sage Ranch Park Info. accessed 6/6/2010
  26. SMMC-Sage Ranch Park Map. accessed 2/28/2010
  27. "Parks -". Retrieved 9 April 2018.
  28. official Santa Susana Pass State Historic Park website. accessed 1/25/2010.
  29. Santa Susana Pass State Historic Park info. accessed 11/22/2009.
  30. "Parks -". Retrieved 9 April 2018.
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