California has led the United States in agriculture for nearly 50 years with a diverse economy of over 250 crop and livestock commodities. With only 4% of the nation's farms and 3% of the nation's farm acreage, the state accounts for over 13% of US gross cash farm receipts. Famous for its specialty crops, California produces virtually all (99% or more) of the following crops grown commercially in the US: almonds, artichokes, avocados, clovers, dates, figs, kiwifruit, olives, persimmons, pistachios, prunes, raisins, and English walnuts. California's total cash farm receipts for 2001 amounted to $25.9 billion.
Agriculture has always thrived in California. The Spanish missions and Mexican ranchos were farming centers until the mid-19th century, when large ranches and farms began to produce cattle, grain, and cotton for the national market. Wheat was a major commodity by the 1870s, when the citrus industry was established and single-family farms in the fertile Central Valley and smaller valleys started to grow large quantities of fruits and vegetables. European settlers planted vineyards on the slopes of the Sonoma and Napa valleys, beginning California's wine industry, which today produces over 90% of US domestic wines. Around 1900, intensive irrigation transformed the dry, sandy Imperial Valley in southeastern California into a garden of abundance for specialty crops. Since World War II, corporate farming, or agribusiness, has largely replaced small single-family farms. Today, the state grows approximately 55% of all fruits and vegetables marketed in the US.
In 2002, California devoted nearly one-third (27.7 million acres/11.2 million hectares) of its 100 million acres (40.4 million hectares) to agricultural production with 84,000 farms comprising 27.7 million acres (11.2 million hectares. One-fourth of all farmland represents crop growth, and currently 10% of all cropland uses irrigation.
Irrigation is essential for farming in California. Agriculture consumes 28% of the state's annual water supply. A major irrigation system was implemented, including the Colorado River Project, which irrigated 500,000 acres (200,000 hectares) in the Imperial Valley in 1913; the Central Valley Project, completed by 1960, which harnessed the runoff of the Sacramento River; and the Feather River Project, also in the Central Valley, which was finished during the 1970s. Largest of all is the California Water Project, begun in 1960 and completed in 1973. During 1983, this project delivered 1.3 million acre-feet of water.
On 16 June 1980, the US Supreme Court ended 13 years of litigation by ruling that federally subsidized irrigation water in the Imperial Valley could not be limited to family farms of fewer than 160 acres (56 hectares) but must be made available to all farms regardless of size; the ruling represented a major victory for agribusiness interests.
The leading crops in 2002 (by value) included greenhouse and nursery products, grapes, and lettuce. These three commodities accounted for 37% of the state's crop receipts that year. Other important crops include cotton, almonds, hay, tomatoes, flowers and foliage, strawberries, oranges, rice, broccoli, walnuts, carrots, celery, and cantaloupe.
California was the top agricultural exporter in the US with $7.7 billion in 1997. Leading agricultural exports in 1998 included vegetables ($1.9 billion), fruits ($1.7 billion), and tree nuts ($1.1 billion). Japan accounts for more than 25% of all California agricultural exports, and the entire Pacific Rim accounts for more than half its total exports. Export markets hold the greatest potential for expanding sales of California agriculture products.