Williamson Act Program Overview


The California Land Conservation Act, better known as the Williamson Act, has its roots in the immediate post-World War II period. During that time California’s agricultural and open space lands began to face dramatically increasing conversion pressures from population growth, new commercial enterprises, and rising property taxes. Valuable farmland began disappearing at an alarming rate as conversion to urban uses became the only financially viable alternative for many landowners. The Williamson Act evolved, and continues to evolve, as a statewide strategic response to these pressures.

In 1965, an interim committee of the California Assembly generated Assembly Bill 2117 (authored by John Williamson). This bill proposed the use of contracts between landowners and local governments to voluntarily restrict development on parcels for a minimum of ten years. Proponents of the legislation felt that contractual restrictions on development would cause property tax assessments to begin leveling off. In practice, however, landowners, assessors, and local governments seemed unconvinced that the restrictive contracts could provide a basis for lower tax assessments. In the two years following passage of the Williamson Act, only 200,000 acres were enrolled under contract in six counties.

The program might have remained small if not for the addition of Article 28 (now part of Article 13) to the state’s Constitution. Article 13 declares the interest of the state in preserving open-space land and provides a constitutional basis for valuing property according to its actual use. The amendment had originated with groups interested in the preservation of open-space land. Agricultural interests added their support after recognizing the importance of a constitutional backing for preferential tax assessments. Article 13 allows preferential assessments for recreational, scenic, and natural resource areas as well as areas devoted to production of food and fiber.

Supporters of the Williamson Act had hoped that financial assistance from the state to local governments would be part of the program. They believed financial support would provide a tangible incentive for local governments to initiate more contracts by partially replacing property tax revenues lost on enrolled land. State funding was provided in 1971 by the Open Space Subvention Act, which created a formula for allocating payments to local governments based on acreage enrolled in the program.

In 1978, the passage of Proposition 13 changed tax assessment practices, limiting valuations to a static base year. Many assumed that this new assessment scheme would severely limit the value of the tax relief offered by the Williamson Act, and that acreage enrolled in the Program would plunge. In fact, however, Proposition 13 has had a negligible effect on Land Conservation Act participation. A study regarding the effects of Proposition 13 on the overall tax benefits of the Williamson Act found that the average tax savings realized as a result of participation in the program had dropped by only about 20 percent. The average tax savings still amounted to as much as 83 percent, depending upon how recently the property in question had changed ownership.

The Williamson Act Program has remained stable and effective as a mechanism for protecting agricultural and open space land from premature and unnecessary urban development. Participation in the program has been steady, hovering at about 16 million acres enrolled under contract statewide since the early 1980s. This number represents about one third of all privately held land in California, and about one half of all the state’s agricultural land. Every indication points to an indefinite continuation of this level of participation into the future.


The Williamson Act is a means to restrict the uses of agricultural and open space lands to farming and ranching uses during the length of the contract period. The Williamson Act Program was also envisioned as a way for local governments to integrate the protection of open space and agricultural resources into their overall strategies for planning urban growth patterns. To this end, three principal objectives were originally outlined:

​Program Structure and Administration

The Williamson Act Program 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. Private land within locally-designated agricultural preserve areas is eligible for enrollment under contract. The minimum term for contracts is ten years. However, since the contract term automatically renews on each anniversary date of the contract, the actual term is essentially indefinite.

Landowners receive substantially reduced property tax assessments in return for enrollment under Williamson Act contract. Property tax assessments of Williamson Act contracted land are based upon generated income as opposed to potential market value of the property. Prior to 2010, local governments received a partial subvention of forgone property tax revenues from the state via the Open Space Subvention Act of 1971.

Contracts may be exited at the option of the landowner or local government by initiating the process of term nonrenewal. Under this process, the remaining contract term (nine years in the case of an original term of ten years) is allowed to lapse, with the contract null and void at the end of the term. During the nonrenewal process, the annual tax assessment continually increases each year until it is equivalent to current tax rates at the end of the nonrenewal period.  Under a set of specifically defined circumstances, a contract may be cancelled without completing the process of term nonrenewal. Contract cancellation, however, involves a comprehensive review and approval process, and the payment of a fee by the landowner equal to 12.5 percent of the full market value of the property in question. Local activities such as eminent domain, or, in some rare cases city annexation, also result in the termination of Williamson Act contracts. For more information on how Williamson Act contracts are removed, visit the Removing Contracts page.

A landowner interested in enrolling land in a contract should contact the jurisdiction in which the land is located (City or County Planning Department) to obtain information and instructions.