St Francis Dam was a huge curved concrete gravity dam that was built in California to regulate and store the reservoirs of water for Los Angeles, California. The reservoir was the main supply of water for the city and as a result, the dam was an integral part of the city’s infrastructure. The dam was located in the San Francisquito Canyon which is found in Sierra Pelona and is about 40 miles from downtown Los Angeles. In fact, it is only 10 miles away from the present-day Santa Clarita.
It was built between 1924 and 1926 with the project being overseen by the chief engineer William Mulholland and commissioned by the Los Angeles Department of Water and Power. Just two years after the structure was completed at around midnight on March 12, 1928, there was a massive failure causing a fatal flood. It is estimated that over 400 people lost their lives during this disaster when the dam collapsed. It is still considered by many one of the worst American civil engineering disasters of the 20th century.
The disaster remains to this day the second greatest loss of life in California, this is after the 1906 San Francisco earthquake and following fire. As you might have guessed, the collapse also marked the end of Mulholland’s career.
When the dam collapsed, the wave was 140 feet high, and moving over 18 miles per hour, it destroyed a Powerhouse whilst taking all the lives of the workmen and their families who lived on site. An hour later a mass of water over 55 feet high was rolling down the Santa Clara River Valley and flooding every town in its path, the sleepy town of Castaic Junction was simply swept away completely by the flooding. One of the reasons there was major casualties was because there were several construction companies on the flats near the Ventura-Los Angeles county line and their workers were in temporary housing during the construction period. No one was able to warn them and these camps were simply swept away by the power of the water, drowning most of the workers.
Bodies were found as far south as the Mexican border, but many were never recovered or even found. This was because much of the water made it out to the Pacific Ocean, sweeping debris and victims into the ocean.