The Simi Hills were inhabited for over 8,000 years by
Paleo-indians and
Chumash-Venturaño Native Americans for settlements and hunting grounds. 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. 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. 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. 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. 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. 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. 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 that it released extensive radiation. More radiation was released in the 1959 event than in the
Three Mile Island accident 20 years later. The groundwater under portions of the Simi Hills, contaminated with toxins and radionuclides that were also historically used at SSFL, has been and is 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. The
Rim of the Valley Trail Corridor is in the planning stages and includes the Simi Hills open space parklands and proposed new areas. ==Parks==