Hidden Hills is an incorporated city, and also a gated development in Los Angeles County, California, United States. The population was 1,875 at the 2000 census. It is located in the westernmost San Fernando Valley. It is one of the wealthiest cities in the United States.
Hidden Hills is in the southern Simi Hills Transverse range near the Santa Monica Mountains, and is located at 34°10′3″N 118°39′39″W / 34.1675°N 118.66083°W / 34.1675; -118.66083 (34.167557, -118.660918).
The city was designed and developed in the 1950s by A.E. Hanson, a renowned Southern California Landscape Architect and planned community developer. His earlier projects included Rolling Hills and Palos Verdes Estates, and the 1920s Beverly Hills Harold Lloyd Estate ‘Greenacres.’ It is a gated residential community with a total all land area of 1.65 sq miles (4.28 km2). An elementary school is publicly accessible at one of the three gates to the community.
Hidden Hills is protected on the north by the nature reserve and greenbelt of the Upper Las Virgenes Canyon Open Space Preserve, a Park with miles of equestrian, hiking, and mountain biking trails. Nearby to the south is the pioneer Leonis Adobe National Historic Landmark, with gardens and a historical Museum. It’s across the historic El Camino Real of the Spanish Las Californias and Mexican Alta California eras, now U.S. Route 101.