The St. Francis Dam was a 200-foot high concrete gravity-arch dam built between 1924 and 1926 in St. Francisquito Canyon (near present-day Castaic and Santa Clarita). The dam collapsed on March 12, 1928 at two and a half minutes before midnight. The resulting flood killed more than 600 residents plus an unknown number of itinerant farm workers camped in San Francisquito Canyon, making it the 2nd greatest loss of life in California after the 1906 San Francisco earthquake. It is considered the worst American civil engineering failure in the 20th century.
About 5 men, 2 dogs, 5 cars, and toboggans in snow, recovering bodies of Charles H. Clark and Edward Walters, with deep snow in foreground, 2 cabin-style buildings at left, 1 with sign reading Lunch Room, with trees and snow-covered hills in background
In November 1933, wildfires raged through the San Gabriel Mountains above the Crescenta Valley. Two floods followed the next year. In late December, a series of storms dropped 12 inches of rain. On New Year's Eve, heavy rains led to sporadic flooding. Around midnight, mountain hillsides collapsed sending millions of tons of mud into the Crescenta Valley neighborhoods below. More than 400 homes were destroyed in La Cañada, La Crescenta, Montrose and Tujunga. Scores of people were killed, and hundreds were left homeless. Another rainstorm on October 17 caused additional flooding and damage, but no deaths.