The Williamson Act: How the Law That Protects California’s Farmland Works

In the decades between the two World Wars,  California’s population grew—but at a reasonable, steady rate. In 1920, two years after the end of World War I, there were 3.4 million people living in the state. By 1940, the year before the United States entered the Second World War, there were 6.9 million. Then the explosion came.

The mid-century population boom may have been good news for industry, and the state’s economy overall. But it was definitely bad news for what was then and now one of the largest sectors of the California economy—agriculture. California’s legislature attempted to address that problem by passing a landmark law that became known as the Williamson Act. 

World War II brought an influx of military service members and workers in the manufacturing industries that supplied and supported America’s fight against the Axis powers. Of all Americans who joined the workforce during the massive wartime industrial mobilization, 40 percent went to work for California’s defense contractors. 

By the time the U.S. and its allies emerged victorious in 1945, California’s population had swelled by another 2.5 million. In the immediate five-year aftermath of WWII, about 2 million more came to California. The population in 1950 reached upwards of 10.5 million. And it showed no signs of slowing down. By 1960 the state grew to 15.7 million people. To get a sense of perspective, from 1958 to 2022 the United States population grew 91 percent. California’s population ballooned by 162 percent. 

The mid-century population boom may have been good news for industry, and the state’s economy overall. But it was definitely bad news for what was then and now one of the largest sectors of the California economy—agriculture. 

In the mid-1960s, California’s legislature attempted to address that problem by passing a landmark law that became known as the Williamson Act. 

How Did the Population Boom Affect Farmland?

In his 2018 study “California’s Evolving Landscape,” UC Davis Agricultural Economics prof Kevin Novan described the state of California’s postwar farmland, and it wasn’t a pretty picture. Rapid suburbanization swallowed up more than a million acres of prime agricultural land between the end of the war and 1968, he reported.

What could the legislature do to keep farmland from disappearing? The Williamson Act was designed to give farmers a reason not to sell—and though the acreage of agricultural land in the state has continued to drop, the law has at least slowed the pace of this loss.

Novan points out that in the year before the U.S. declared war on Japan and Germany in the wake of the Pearl Harbor attack, the population of the city of San Francisco was 634,536. That was nearly twice the populations of three nearby counties—Santa Clara, Contra Costa and San Mateo—combined. One decade later, in 1950, those three counties had a combined population 50,000 more than San Francisco. And in the subsequent three decades, the population of those three counties kept right on growing, while San Francisco’s contracted. 

People were moving to the suburbs. As they were throughout the United States, where (as of 2018) 52 percent of people describe themselves as living in the suburbs compared to just 13 percent before WWII.

At the beginning of all this movement, there were no suburbs. They had to be built somewhere—and the only place to build them was open land, which was mostly farmland. As a result, California farmland that was always a high-priced commodity went through the roof. In the year leading up to WWII, according to Novan’s research, agricultural land in the state cost $700 more per acre than the national average, thanks mainly to the land’s productivity and amenability to “high-value crops.”

From the years 1955 to 1965, however, the average price of an acre shot up by an eye-popping 285 percent, to $2,000. And it wasn’t because the price of apricots went up. It was a matter of supply and demand. The demand for land went up as new Californians as well as some previous city-dwellers moved to suburban areas and big developers hoovered up the land owned by farmers.

The boost in neighboring land values wasn’t necessarily a bonanza for farmers, who faced sharply increased property taxes. As their tax bills swelled and developers with open wallets came calling, California farmers had little incentive to hold on to their land. From 1950 to 1993, the amount of agricultural land in the state dropped from 38 million acres, to 29 million.

What could the legislature do to keep farmland from disappearing? The Williamson Act was designed to give farmers a reason not to sell—and though the acreage of agricultural land in the state has continued to drop, the law has at least slowed the pace of this loss.

What is the Williamson Act?

As California’s postwar population and economic booms kept right on going, even with the Allied victory two decades in the rear-view mirror, the legislature scrambled for ways to put the brakes on the steady disappearance of farmland. In 1965, Assemblymember John C. Williamson, a then-53-year-old Oklahoma native and former owner of three Bakersfield gas stations—who came into office thanks to California’s 1958 Democratic landslide election—authored a bill he titled the California Land Conservation Act. 

In the first two years of the Williamson Act’s existence, a mere 200,000 acres in just six counties were placed under the conservation contracts.

The bill, which came to be identified by Williamson’s name, allowed local governments to enter into contracts with landowners within their jurisdictions to keep their land out of the hands of developers for at least 10 years. That way, farmland would stay farmland, with the added benefit of keeping open space uncluttered by suburban housing.

The law did not ban homebuilding completely, but any houses built on the contracted land must be consistent with agricultural use, and there must be an ongoing agricultural operation on the land where the house goes up.

With the value of their land skyrocketing, why would farmers want to enter into such contracts? Because by foregoing development, the valuations of their land remained relatively constant. That means property taxes on the land would also remain at manageable levels because it would be assessed based on its actual use, not its market value. Or so the theory went.

Farmers weren’t buying it. In the first two years of the Williamson Act’s existence, a mere 200,000 acres in just six counties were placed under the conservation contracts. In 1969, the law was amended to make the requirement that land would be valued based on what it was actually used for rather than on its potential for development a legal requirement, not just a hope.

That gave farmers a strong incentive to sign Williamson Act contracts—lower taxes. Who doesn’t like those? But it gave local governments a disincentive. By placing land under the provisions of the act, they lose potential property tax revenue, one of the most important sources of funds for any local government.

In 1971, the legislature passed the Open Space Subvention Act (OSSA), which allowed the state to pay local governments to make up for some, if not all of the lost tax revenue. From 1972 to 2010—when OSSA payments were scratched from the state budget—local governments received more than $863 million from the program.

The Williamson Act Today

Since those initial 200,000 acres went under contract in the first two years of the Williamson Act, the law has become far more widely used, thanks to the legislative updates. Today, about 16 million acres are protected by Williamson Act contracts. That’s more than half of the approximately 30 million agricultural acres in the state, and roughly one of every three acres of privately held land in California.

Though the contracts restrict land from development, they do not prevent landowners from selling. But buyer beware. The contracts are attached to the land, not to any individual owner. That means the new owner of a property under a Williamson contract remains bound by the terms of that contract until it expires.

And when is that? 

Most contracts come with 10-year terms, though some jurisdictions require 20-year contractual commitments. The contracts, however, renew automatically for one-year extensions indefinitely—unless the landowner initiates a non-renewal process. That doesn’t happen overnight. Non-renewal requires nine years notice. 

Once a landowner files for non-renewal, the tax valuation of the contracted property goes up every year for nine years, until it reaches the current market value—marking the end of the Williamson Act contract.

Landowners can also apply to cancel their contracts, which would be a quicker way of getting out from under the law’s non-development restrictions. In fact, landowners could get a decision in 30 days. But the state strongly prefers that they use the non-renewal process first, and according to the California Government Code, cancellations can be granted only for properties already under a non-renewal filing. 

The contracts can then be canceled only if specific requirements are met. Among those conditions, the new proposed use of the property must be in the “public interest,” and the cancellation will not allow “discontiguous urban development.”