Calabasas is an affluent city in Los Angeles County, California in the western United States. It is located in the southwestern San Fernando Valley and the Santa Monica Mountains. As of the 2000 census, the city population was 23,123. The city was formally incorporated in 1991. The Leonis Adobe, an adobe structure in Old Town Calabasas, dates from 1844 and is one of the oldest buildings in the greater LA area. An extensive 2006 Secondhand Smoke Control Ordinance caused the city to receive international attention.