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, and average around 7 mi north-south. The Simi Hills are part of the central Transverse Ranges System. They lie almost entirely withi…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, and average around 7 mi north-south. 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.