Measured by yearly production, the San Joaquin Valley is one of the highest-value stretches of farmland in the country, and is dominated by large growers who preside over a labor force of migrant workers in a way that has not changed much since Carey McWilliams described it in his 1939 book, Factories in the Fields. The Fresno-based writer Mark Arax likens it to a Central American country. “It’s the poorest part of California,” he told me. “There’s almost no middle class. To find its equivalent in the United States you’d have to go to Appalachia or the borderlands of Texas.”