The city is adjacent to Thousand Oaks, Moorpark, and the Los Angeles neighborhood of Chatsworth.
The city's 2014 population has been estimated at 126,871, up from 111,351 in 2000.
It was one of the largest lands, but later when Mexico became independent from Spain, land was handed out much more freely.
The Simi Adobe-Strathearn House, later the home of Robert P.
The small colonial town known as "Santa Susana del Rancho Simi" throve in the late 19th century and had a Spanish-speaking majority, but since then many Anglo-Americans have arrived to settle.
Farms, orchards and groves dominated the valley's landscape until the 1970s.
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 2,848 acres (1,153 ha) Santa Susana Field Laboratory located in the Simi Hills, was used for the development of pioneering nuclear reactors and rocket engines beginning in 1948.
The site was operated by Atomics International and Rocketdyne (originally both divisions of the North American Aviation company).
in the eponymous valley, is situated in the southeast corner of Ventura County, California, United States.
30 miles (48 km) from Downtown Los Angeles, Simi Valley is part of the Greater Los Angeles Area.
The Ronald Reagan Presidential Library, where the former president was buried following his death in 2004, is in Simi Valley.