The San Joaquin Valley was not settled in any considerable way until the mid-19th century. Spanish explorers, setting off from missions and ports to the west, had passed through the area starting at least two centuries prior. However, the valley wasn’t on any important trade routes. Given the hot, arid climate, it wasn’t the easiest place to live, farm or ranch.

The Gold Rush of 1849 made the San Joaquin Valley a much more interesting location though. It was near enough to the gold fields to be a practical source of wine grapes and several other food products. And it also was on the way to those fields from ports on California’s southern and central coast. So, suddenly, major trade routes did pass through.

Still, due to the very dry climate, most agriculture failed to thrive—especially in the southern half of the valley—until irrigation became possible in the 1880s. Then, with water readily available, the valley’s deep, fertile soils became very attractive indeed. Initially, as in other areas of California, wheat was the most important crop. But, as demand for California wheat declined and canning, drying, and transport technologies improved, fruit crops began to grow in importance. In ten years, from 1880 to 1890, vine (wine, table, and raisin grapes) acreage in the valley rose from 682 ha to 26,033 ha (1,765 to 64,330 acres). The share of state vine acres expanded from 4% to 38%.2

Prohibition had a severe impact on wine production throughout California. However, some San Joaquin Valley vineyards did well by selling uncrushed grapes to home winemakers. That’s because total U.S. wine production actually rose during Prohibition, though 90% of the total was accounted for by home winemakers.1 So, San Joaquin Valley grapes were shipped all over the country. By 1925, San Joaquin Valley accounted for 72% of the state’s vine acreage. 

To meet this demand with a product less sensitive to shipping conditions, and to use excess grapes, large-scale  production of grape concentrate began in the late 1920s. Since it is concentrated juice with no alcoholic content, its production was not subject to Prohibition’s 200-gallon limit: home winemakers simply had to add water and yeast.

With Repeal, wineries were once again allowed to produce commercial quantities of wine. However, public tastes had changed. Whereas pre-Prohibition sales were mostly of dry wine, consumers liked it sweet now. This was advantageous to the San Joaquin Valley, which had the warmth, sun, and fertile acres to produce grapes ripe enough to make large amounts of sweet wine. In fact, San Joaquin Valley already had a long history with sweet wines—production had skewed heavily toward them even before Prohibition.

One Lodi winery, The Roma Wine Company, was particularly well positioned to capitalize on this. During Prohibition, it had built a thriving business producing sacramental and “medicinal” wine, which were allowed by law. So it was that, in 1933, many considered it the biggest, and perhaps most technically advanced, winery in the country. In 1935, Roma expanded, adding a larger winery with its own bottling line in Fresno.

But Roma was far from the only major wine company to spring out of the San Joaquin Valley at this time. Ernest and Julio Gallo, while still attending high school in Modesto, began growing and selling grapes to home winemakers during Prohibition. They started making and selling their own wine in 1933. Today, still based in Modesto, Gallo is the largest wine company in the world.

Wine and grape cooperatives also became big business. Family-owned Petri Wine Company expanded post-Prohibition, in part by buying other producers, including Italian Swiss Colony. The multi-brand group was reorganized into a cooperative, United Vintners. In 1954, Louis Petri sold that to Allied Grape Growers, another cooperative the company was affiliated with and the biggest in the country at that time. 

As demand for San Joaquin Valley grapes grew, mechanization in the vineyard became an important enabler of the necessary expansion of vine acres. Advances in agricultural equipment came rapidly in the 1950s, first for other crops and then, eventually, for wine grapes. The valley is an ideal location for mechanical vine maintenance and harvesting because vineyards are generally flat and can be planted to straight rows with wide spacing. And, given the size of some vineyards, it would be impossible to hand-harvest all the grapes at the opportune moment. There aren’t nearly enough workers to do that.

Still, field workers are, and have always been, crucial to San Joaquin Valley grape growers. It was there, in the table grape fields, that the United Farm Workers went on strikes beginning in 1965. Led by Cesar Chavez, Dolores Huerta and others, these strikes, and also boycotts, brought the UFW to national attention. They also resulted in the Agricultural Labor Relations Act of 1975, which granted all California agricultural workers the right to organize. Many other laws focused on protection of agricultural workers followed.

San Joaquin Valley’s importance within the California wine industry has continued to grow in terms of acreage and production. The annual crush within the valley in 2018 was roughly 3.5-times that of all other regions combined. And, of course, the valley is home to many of the country’s largest wine companies.

The most important AVA in the San Joaquin Valley is Lodi. See the Lodi module for an excellent overview of that region’s viticultural history.