The history of agriculture in California began with California's indigenous peoples and was radically altered by colonization and statehood. Throughout its history agriculture has formed an important part of the state's economy.

Peake & Fleure 1927 propose that many crop wild relatives and a climate with both a rainy season and a dry season are necessary for an area to become a center of agriculture.^[1]: 8 Before human arrival a wide variety of crop wild relatives (CWRs) were already found here – and although most of land has a monotonously desert or near-desert rain supply – some has a climate type called Mediterranean.^[1]: 8

Since initial contact between Europeans and Indigenous American peoples, the topic of Native American agriculture has been debated. While agriculture in pre-contact California certainly did not fit into the Western definition of agriculture, the keen stewardship of California's natural ecosystem by Indigenous Californians to achieve the best possible output of resources is "agricultural," with California's ecosystems acting as a large, unbounded agricultural site.^[2][3] Because of this difference in ideology, agricultural practices in pre-contact California often took a different form than those of Europe.

Some California hunter-gatherer tribes, including the Owens Valley Paiute, developed irrigation.^[4] Native Californians were skilled at gathering materials from plants at all times of the year, allowing the consistent gathering of materials from any and all local plants. Depending on when various plants—including succulents, flowers, and trees—bloomed or became ripe, different aspects of the plant could be accessed or harvested by Native California peoples.^[5]

Native Californians also developed strategies when it came to competing with animals for resources. The Kashaya Pomo, for example, timed their harvest of dogwood to be before insects and worms would be able to access the inner parts of the plant.^[5] Indigenous Californians also developed strategies for acquiring black oak acorns directly from tree branches using a long pole, increasing harvest yields that would otherwise have been disturbed by animals.^[5]

Black oak acorn harvests were further increased by cultural burning, which stimulated acorn growth and increased biodiversity in the area.^[6] Cultural burning was commonly practiced by throughout California to maintain a healthy landscape that produced quality resources, as the Karuk, Yurok, Hupa peoples all regularly burned areas of bear grass and California hazelnut and to encourage the growth of stronger stems that could be used for basketry.^[7][8]

In the late 1700s, Franciscan missionaries established Spanish missions in California. Like earlier Spanish missions established in Baja California, these missions were surrounded by agricultural land, growing crops from Europe and the Americas, and raising animals originating from Europe. Indigenous workers from Baja California made up a large part of the initial labor force on California missions.^[9] In the early 1800s, this flow of laborers from Baja California had largely stopped, and the missions relied on converts from local tribes. By 1806, over 20,000 Mission Indians were "attached" to the California missions. As missions were expected to become largely self-sufficient, farming was a critically important Mission industry. George Vancouver visited Mission San Buenaventura in 1793 and noted the wide variety of crops grown: apples, pears, plums, figs, oranges, grapes, peaches, pomegranates, plantain, banana, coconut, sugar cane, indigo, various herbs, and prickly pear.^[10] Livestock was raised for meat, wool, leather, and tallow, and for cultivating the land. In 1832, at the height of their prosperity, the missions collectively owned over 150,000 cattle and over 120,000 sheep. They also raised horses, goats, and pigs.^[11]

While the Spanish were the most successful farmers active in California in the early 1800s, they were not the only ones. In 1812, the Russians established Fort Ross in what is now Sonoma County, California, and intended the fort in part as an agricultural supply point for other Russian activity on the west coast. Despite Russian plans for the colony, agriculture at Fort Ross had low yields, significantly lower than the California missions. Inefficient farming methods, labour shortages, coastal fog, and rodents all contributed to limit agriculture at the fort.^[12]

The Spanish (1784–1810) and Mexican (1819–1846) governments made a large number of land grants to private individuals from 1785 to 1846. These ranchos included land taken from the missions following government-imposed secularization in 1833, after which the missions' productivity declined significantly. The ranchos were focused on cattle, and hides and tallow were their main products. There was no market for large quantities of beef (before refrigeration and railroads) until the California Gold Rush.

In 1848, before the Gold Rush, the population of CA was approximately 15,000, not counting Native Americans. By 1852, there were over 250,000 people in the state.^[13] and by 1870, 560,000 people.^[14] This rapid population growth drove an increase in importation of agricultural products, and, within a few years, a massive growth in in-state agriculture. In the first years of the gold rush, the state relied on agricultural imports arriving by ship, from Australia, Chile, and Hawaii. During these years, there was rapid growth in vegetable farming for local markets. This was followed by an expansion of grain farming.^[13] A shift in the economic dominance of grain farming over cattle raising was marked by the passage of the California "No-Fence Law" of 1874. This repealed the Trespass Act of 1850, which had required farmers to protect their planted fields from free-ranging cattle. The repeal of the Trespass Act required that ranchers fence stock in, rather than farmers fencing cattle out. The ranchers were faced with either the high expense of fencing large grazing tracts or selling their cattle at ruinous prices.^[15][16] By the 1890s, California was second in US wheat production, producing over one million tons of wheat per year,^[13] but monocrop wheat farming had depleted the soil in some areas resulting in reduced crops.^[17]

Irrigation was almost nonexistent in California in 1850, but by 1899, 12 percent of the state's improved farmland was irrigated.^[17]

Luther Burbank moved to Santa Rosa, California in 1875, and developed numerous commercially successful varieties of plants over the next 50 years.

The 1902 Newlands Reclamation Act funded irrigation projects on arid lands in 20 states including California.

In 1905, the California legislature passed the University Farm Bill, which called for the establishment of a farm school for the University of California (at the time, Berkeley was the sole campus of the university).^[18] The commission took a year to select a site for the campus, a tiny town then known as Davisville.^[18] UC Davis opened its doors as the "University Farm" to 40 degree students (all male) from UC Berkeley in January 1909.

In 1919, the California Department of Food and Agriculture was established. The department covers state food safety, state protection from invasive species, and promoting the state's agricultural industry.

The Dust Bowl of the 1930s drove many people from the American prairie, and a significant number of these economic migrants relocated to California. Poor migrants from Oklahoma and nearby states were sometimes referred to as Okies, generally a pejorative term. In 1933, the state saw a number of agricultural labor strikes, with the largest actions against cotton growers. Cherry, grape, peach, pear, sugar beet, and tomato workers were also involved.

In 1942, the United States began the Bracero program. Lasting until 1964, this agreement established decent living conditions and a minimum wage for Mexican workers in the United States.

In 1965, the Williamson Act became law, providing property tax relief to owners of California farmland and open-space land in exchange for agreement that the land will not be developed.

The 1960s and 1970s saw major farm worker strikes including the 1965 Delano grape strike and the 1970 Salad Bowl strike. In 1975, the California Agricultural Labor Relations Act of 1975 was enacted,^[19] establishing the right to collective bargaining for farmworkers in California, a first in U.S. history.^[20] Individuals with prominent roles in farm worker organizing in this period include Cesar Chavez, Dolores Huerta, Larry Itliong, and Philip Vera Cruz.

In the late 1980s the Ives flower ranch was the site of a notorious employment case.^[21] This ranch was in Ventura and involved Mixtec farm workers (from the southern Mexican state of Oaxaca) and illegal employment conditions.^[21] The ranch paid $1.5 million in unpaid wages and fines.^[21]

Through 1995 there were 50,000 Mixtecs every year in California agriculture.^[21] They were about 70% of the 10,000 agricultural laborers in San Diego County, and had been spreading northwards to also work in Oxnard, Santa Maria and Madera County, and even into Oregon and Washington.^[21] They were usually not the only indigenous Mexican ethnic groups – Zapotecs and Mayans were also usually working the same jobs.^[21] In the 1990s it was common to arrive in Arizona first, work on an Arizonan farm, and then move here.^[21]

In the 2000s and 2010s, Californians voted for propositions which established new protections for farm animals. 2008 California Proposition 2 and 2018 California Proposition 12 both established minimum requirements for farming egg-laying hens, breeding pigs, and calves raised for veal. Few veal and pig factory farm operations exist in California, so these propositions mostly affect farmers who raise California's 15 million egg-laying hens.^[22]