The city of Los Angeles grew tremendously between its incorporation in 1850 and the turn of the 20th century (and ever since). There was never enough fresh water for the growing city, so William Mulholland designed aqueducts and several dams to supply L.A. This included the St. Francis Dam, which held over 12 billion gallons of water. The massive construction was completed in 1926. And it came in under budget.
It was three minutes before the stroke of midnight on a windy March 12, 1928, when the St. Francis Dam broke. Many of the sleepy residents of the San Francisquito Canyon mistook the shaking and rumbling for an earthquake, a common enough occurrence in Southern California. Within moments, the canyon was filled with 12.6 billion gallons of water, which had been intended for the sinks, bathtubs, and residents of Los Angeles 47 miles away. The water instead roared through the canyon, valley, and the small towns that populated the region, smashing everything in its path.
No one who saw the dam break lived to tell about it. The water swept away several towns on its path to the ocean 55 miles away. It is believed that over 600 people were killed in the disaster. And just about everyone blamed one man: William Mulholland. Smithsonian tells the story of the dam, the disaster, and the investigation into what went wrong at the St. Francis Dam.