At just three minutes before midnight on March 12, 1928, the St. Francis Dam, which had been designed as a reservoir for the Los Angeles water supply by William Mulholland, suddenly failed, releasing 11 billion gallons of water into a narrow valley in northeastern Los Angeles County, destroying everything in its path. Over the course of the next four hours, a roaring wall of water swept through the night, traveling 55 miles from the San Francisquito Valley, through the Santa Clara Valley, and on to the Pacific Ocean.