In 1965, the State legislature established the California Land Conservation Act, or Williamson Act (Government Code Section 51200 et. seq.). The Williamson Act enables local governments to enter into contracts with private landowners for the purpose of restricting specific parcels of land to agricultural or related open space use. In return, landowners receive property tax assessments that are much lower than normal because they are based upon farming and open space uses as opposed to full market value. A contract is required to have a minimum 10-year term, with the term extending by one year on the anniversary date of the contract each year until a notice of non-renewal is filed pursuant to Government Code Section 51245, or the contract is cancelled pursuant to Government Code Section 51250. This creates a rolling 10-year contract. Either a local agency or the property owner may terminate the agreement by executing a nonrenewal, which establishes the final 10-year period for the contract. A contract may also be cancelled immediately, subject to payment of a penalty fee by the property owner.

The Williamson Act requires that, prior to the establishment of a contract, a local agency first establish an agricultural preserve. Only properties that are within the preserve may enter into a contract. Some local agencies, such as Sacramento County, establish the preserve co-terminus with the proposed contract boundaries, creating a 1:1 relationship. Other counties, such as Merced and Stanislaus, have applied preserves to all properties designated in their General Plan for agriculture.

While a Williamson Act contract provides the most protections for agricultural activities, including limiting the range of allowed uses in a way that is more restrictive than zoning, the application of a preserve also carries certain protections. Land within a preserve is limited in the types of subdivisions and land transactions that may occur. The intent is to limit subdivisions or transactions that would take a site out of agricultural production.

Contracts and preserves established by a county transfer to a city upon annexation and the city becomes the successor agency in interest pursuant to Government Code Section 51235.

The City has establishedRules for the Administration of Agricultural Preserves and the Implementation of the California Land Conservation Actas required by State law.