Calabasas is an affluent city in Los Angeles County, California in the western United States. It is located in the hills in the southwestern San Fernando Valley and the Santa Monica Mountains between Woodland Hills, Agoura Hills, West Hills, and Malibu, California. As of the 2010 census, the city population was 23,058, up from 20,033 at the 2000 census, according to the U.S. Census Bureau website, factfinder.census.gov. The city was formally incorporated in 1991. Prior to that the area was an unincorporated portion of Los Angeles County.