Contra Costa County has been implementing the Williamson Act since 1968 when the Board of Supervisors adopted Ordinance 68-53, which authorized the creation of Agricultural Preserves and the execution of Land Conservation Contracts pursuant to state law.
The Department of Conservation governs the program at the state level. The program is administered locally, through a combined effort of the Assessor's office, planning staff in the Community Development Department, and County Counsel. The Assessor determines the value of the land under contract with a restricted value, based on income capability rather than market value, giving tax relief to property owners.