Simi Valley (sē`mē, sĭm`ē), city (1990 pop. 100,217), Ventura co., SW Calif. in an oil, fruit, and farm region; laid out 1887, inc. 1969. Highly residential, the city also produces a variety of light manufactures, including electrical, electronic, computer, and medical equipment; clothing; metal and plastic products; and furniture. The population of Simi Valley more than doubled between 1970 and 2000, with the growth of the Los Angeles metropolitan area. Of interest are a historical park, Native American caves, and the old stagecoach road.