It is widely believed that water is badly misallocated in California because it is mispriced, resulting in too much agricultural use. At the same time, however, California’s groundwater “problems”—declining water tables, compactification, polluted farmland, and subsidence—seem to arise from the fact that farmers often find it cheaper to pump water than buy it even at subsidized rates. Seems puzzling. Economists and journalists have been saying these things since I was a graduate student. To a political scientist, it is even more puzzling that a small bunch of farmers and ranchers could cause so much trouble…. And for so long. In this paper, I show that the arid parts of the state—especially in the Southern Central Valley—have generated a small number of distinctively large and vertically integrated organizations, dependent on control of groundwater, which have often played pivotal roles in shaping political deals. These critical deals include the formation of the state’s peculiar water law in the late 19th century, the building of the federal and then the state water projects, and the responses to environmental demands for water.