The California Land Conservation Act of 1965, better known as the Williamson Act, created a program to help counties preserve agricultural land and open space by offering a tax incentive to property owners. The Act provides an arrangement where private landowners voluntarily restrict their land to agricultural and compatible open space uses under a contract with the County, known as a Land Conservation Contract.
The Williamson Act contract is an enforceable restriction on land and is binding on successors to both the landowner and the local government. The minimum term for a contract is ten years, and the contract is automatically renewed annually, unless either party gives advance notice of non-renewal or the contract is canceled.
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.