Photo, looking north, shows what was left of the St. Francis Dam shortly after it failed on March 12, 1928.
Photograph by Los Angeles Times staff photographer George Watson. (George Watson is the great-uncle of Signal newspaper photographer Dan Watson, who co-manages the famous Watson Family Photographic Archive.)
Seven miles up San Francisquito Canyon Road from today's Copper Hill Drive, construction on the 700-foot-long, 205-foot-high St. Francis Dam started in August 1924. With a 12.5 billion-gallon capacity, the reservoir began to fill with water on March 1, 1926. It was completed two months later.
At 11:57:30 p.m. on March 12, 1928, the dam failed, sending a 180-foot-high wall of water crashing down San Francisquito Canyon. An estimated 431 people lay dead by the time the floodwaters reached the Pacific Ocean south of Ventura 5½ hours later.
It was the second-worst disaster in California history, after the great San Francisco earthquake and fire of 1906, in terms of lives lost — and America's worst civil engineering failure of the 20th Century.