Construction of the St. Francis Dam, a unit of the Los Angeles Aqueduct, began on this site in August 1924. When completed in May 1926, the concrete dam stood 185 feet above the stream bed and impounded a 610 surface-acre lake. At 11:57½ P.M. on March 12, 1928, the dam collapsed, causing the second greatest disaster in the state of California. At least 425 lives were lost in the 3½ hours it took the released water to travel 54 miles down the Santa Clara River Valley to the sea at Ventura.