The Rocketdyne division developed a variety of liquid rocket engines.Rocket engine tests were frequently heard in Simi Valley.Other areas containing Chumash Native American pictographs in the Simi Hills are for instance by Lake Manor and Chatsworth.
The city sits next to Thousand Oaks, Moorpark, and Los Angeles.
The city's 2014 population has been estimated at 126,871, up from 111,351 in 2000.
A few years after Jose de la Guerra's death in 1858, the rancho was sold to the Philadelphia and California Petroleum Company headed by Pennsylvania Railroad president, Thomas A. When no great amount of oil was discovered, Scott began to sell the rancho.
In 1887, a portion of the rancho was bought by a newly formed company, the Simi Land and Water Company.
Strathearn, served as the headquarters of the rancho.
José de la Guerra y Noriega, a Captain of the Santa Barbara Presidio, who had begun to acquire large amounts of land in California to raise cattle, purchased Rancho Simi from the Pico family in 1842.
There was also a great deal of destruction caused by a flood in 1952.
The city incorporated as Simi Valley in 1969, when the area had only 10,000 residents.
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 is largely a commuter bedroom community, feeding the cities in the Los Angeles area and the San Fernando Valley to the east, and cities in Ventura County to the west.
There are many Chumash cave paintings in the area containing pictographs, including the Burro Flats Painted Cave in the Burro Flats area of the Simi Hills, located between the Simi Valley, and West Hills and Bell Canyon.