The Centennial Specific Plan first began as a vision filed with LA County Planning in 2002. After more than 16 years of review by the County and other local, state and federal agencies and departments, as well as considerable public input given at community meetings and public hearings, the Specific Plan was adopted by the LA County Board of Supervisors on April 30, 2019 and became effective on May 30, 2019. The Specific Plan authorizes the development of a new master-planned community of 19,333 residences and 8.4 million square feet of commercial and business park uses, with associated grading, utilities, infrastructure, public services and facilities, and offsite infrastructure and mitigation areas. The buildout timeframe for Centennial is approximately 20 years from the initial groundbreaking. Once fully built-out, the population is estimated to be 57,000 people.
The Centennial site is located in the upper northwest corner of Los Angeles County, adjacent to Kern County, where the southern end of the Tehachapi Range meets the northern reach of the San Gabriel Mountains. Centennial is a part of the wider Tejon Ranch property. At approximately 270,000 acres (422 square miles), Tejon Ranch is the largest expanse of private land in California under a single ownership. Over 90 percent of the Ranch will remain as open space under a Ranch-wide conservation agreement signed by multiple environmental organizations in 2008. Information about the management of conservation lands within the Tejon Ranch can be found at the Tejon Conservancy.