The Cucamonga Valley AVA is an American Viticultural Area in San Bernardino County, California, about east of Los Angeles. Grape cultivation began in the Cucamonga Valley in 1838, and quickly became a major agricultural crop for the area. When Prohibition began in 1920, the Cucamonga Valley produced more wine grapes than Napa County and Sonoma County combined. Following Prohibition, the wine industry and other agricultural endeavors in the Cucamonga Valley faced increasing pressure from the urban expansion of Los Angeles and Orange County. Cucamonga Valley is a hot climate for viniculture, with summer temperatures often exceeding . The valley floor is sandy, alluvial soils. Pierce’s disease has affected vines in the valley.