Origins of grapes, wine, and raisins in the U.S.

Spanish missionaries introduced grape-growing and winemaking knowledge to Mexico, California, and other parts of the United States in the 18th century. In addition to fresh grapes and wine, missionaries also made raisins from Muscat grapes. Eventually, due to its long hot growing season and abundant water supply, the San Joaquin Valley became the most desirable location for raisin production.

Source: https://www.agmrc.org/commodities-products/fruits/raisins