Minutes before midnight on March 12, 1928, the St. Francis Dam collapsed, sending more than 12 billion gallons of water surging through California's Santa Clara Valley and killing some 400 people, causing the greatest civil engineering disaster in twentieth-century American history. This extensively illustrated volume gives an account of how the St. Francis Dam came to be built, the reasons for its collapse, the terror and heartbreak brought by the flood, the efforts to restore the Santa Clara Valley, the political factors influencing investigations of the failure, and the effect of the disaster on dam safety regulation. Underlying all is a consideration of how the dam-and the disaster-were inextricably intertwined with the life and career of William Mulholland.