In the early hours of March 13, 1928, one of the greatest technical disasters in American history occurred in California. The St. Francis Dam, a symbol of engineering ambition and rapid development in Los Angeles, suddenly collapsed.
The Construction Journey and Disaster
More than 52 million tons of water rushed down the Santa Clara Valley overnight, sweeping away homes, claiming the lives of over 400 people, and leaving behind terrible consequences for both human lives and the environment. This was not only a tragedy but also a costly lesson about responsibility and caution in engineering projects.
The Construction Journey and Warning Signs Ignored
St. Francis Dam. (Photo: Getty Images).
As California attracted people from the East to Los Angeles in the early 1900s, the city’s population exploded, while its drinking water supply dwindled. With an insatiable desire for growth, city leaders authorized William Mulholland, chief engineer and general manager of the Los Angeles water system, to construct the Los Angeles Aqueduct, inaugurated in 1913, which diverted water from the Owens Valley across 370 km of desert.
However, even the aqueduct could not save this thriving city, where the population surged from over 100,000 in 1900 to over 1 million in the 1920s. A nearly record-low rainfall that lasted seven years combined with the city’s exponential development jeopardized the water supply.
To prevent Los Angeles from drying up, Mulholland built a storage system to reserve water. The most ambitious part of the project was the St. Francis Dam, located 75 km northwest of downtown Los Angeles. Completed in May 1926, this concrete arch dam stood 64 meters tall and could hold over 12 billion gallons of water (approximately 45 billion liters), enough to supply the city for a year. The dam became a symbol of Los Angeles’ development and a source of pride for Mulholland, who was hailed as the city’s “savior.” However, throughout the construction and operation, concerning warning signs were ignored.
In March 1928, winter rains prompted Mulholland to announce that all irrigation activities would be halted for a few days, a move that would save millions of dollars. The rain caused the reservoir behind the St. Francis Dam to reach maximum capacity. During a daily inspection of the concrete barrier on the morning of March 12, 1928, the dam’s caretaker, Tony Harnischfeger, became alarmed when he noticed a significant leak on the western edge, which could indicate that the foundation material was being washed away from beneath the dam.
Upon being informed, Mulholland came to inspect and deemed it a normal phenomenon caused by nearby construction projects. With absolute confidence in his structure, he left without taking any precautions.
“There were observations of the leak, but it was considered insignificant. However, it was a sign that the dam was in trouble,” said William Deverell, a history professor and co-director of the Huntington-USC Institute for California and the West.
While Mulholland trusted the integrity of the dam, rancher Chester Smith grew increasingly wary. While tending to cattle that day, he noticed a significant leak on the western side of the barrier, with water spraying over the top. Downstream from the dam, Smith went to bed with a sense of anxiety, leaving the door open in case he needed to escape quickly.
The Horrific Disaster in the Darkness
At 11:57 PM on March 12, 1928, the St. Francis Dam suddenly collapsed. In the darkness, a water column over 42 meters high surged down the San Francisquito Canyon at a speed of 29 km/h. This artificial tsunami swept away everything in its path: homes, roads, orchards, and railway tracks.
The ground north of Los Angeles began to tremble. Houses shook. Windows rattled. A large section of the dam shattered. A massive amount of water with tremendous pressure began to gush through the created gap. Just two and a half minutes before midnight, the hillside immediately east of the dam was completely flattened.
In a chain reaction, the dam’s breach grew larger, and the land to the west quickly met the same fate. In the dark, there were no warning signals; the dam, built in a stepped design, collapsed with a terrifying flood.
Residents living near the mountains were the first to feel the unsettling tremors of the ground and had no time to react before the waves surged in.
By about 12:45 AM on March 13, 1928, the flood—later described by survivors as a “huge black wall”—had left San Francisquito Canyon, quickly heading west towards the Santa Clara River Valley, where 10,000 residents were peacefully asleep.
Awakened by barking dogs, Smith heard a rumble and immediately ran to higher ground while shouting warnings to his family. Those precious moments saved his life, but hundreds of others were not so fortunate.
Living 800 meters downstream, Harnischfeger, his girlfriend, and their 6-year-old son could have been among the first victims, although the bodies of the two were never found. The flood killed 65 employees and family members at a nearby power plant, 84 workers from Southern California Edison sleeping in tents at a construction camp, and dozens of Mexican migrant fruit pickers in the area were also unable to escape.
The massive wave crashed into the victims, stripping them of their clothes and leaving them bruised and torn. It took months to collect bodies from the debris and mud.
The raging floodwaters were not only deadly but also devastated the environment. It carried away rocks, trees, and even human remains all the way to the Pacific Ocean. Bodies washed ashore as far as San Diego, making identification and accurate death toll estimation exceedingly difficult. Official reports estimated fatalities at 400, but the actual number could be much higher.
A Costly Lesson
Remnants of the St. Francis Dam. (Photo: Getty Images).
Mulholland mournfully stated: “This investigation is a very painful thing for me to attend.” He expressed a desire to die like the victims to avoid standing trial after the disaster. The chief engineer testified that he saw no signs indicating the dam would fail.
The investigation exonerated Mulholland, but the ruling stated that the construction and operation of a large dam should never be left to a single person’s decision without scrutiny from an independent authority, no matter how renowned that person may be.
A commission of engineers and geologists appointed by California Governor C.C. Young concluded that the substrate beneath the western abutment was not strong enough to support this massive structure, and water had seeped into the St. Francis Dam’s foundation, raising it up. Investigators uncovered other design flaws, including raising the dam from an initially proposed height of 55 m to 64 m without increasing the corresponding base width to enhance load-bearing capacity, significantly reducing the structural stability. Additionally, geological studies found that the eastern abutment was even located on an area that had previously experienced a landslide and showed signs of potential landslides, which Mulholland did not detect.
Professor Deverell stated: “The geological structures on both sides of the dam were different, and that created the potential for catastrophic failure.” He concluded that due to Mulholland’s peak of fame, power, and authority, there was less emphasis on checking and balancing to ensure quality and safety of the dam.
The disaster ruined Mulholland’s reputation, forcing him to resign shortly afterward. He spent his final years in deep regret, burdened by the consequences of his mistakes.
The St. Francis Dam disaster not only claimed the lives of hundreds but also served as a major shock to the construction engineering industry. The lessons learned from this event completely changed safety standards in the design and operation of water infrastructure in the United States. Consequently, large projects now require the involvement of multiple experts from various fields and strict oversight from independent authorities. The design of large structures, especially dams, must carefully consider geological factors to avoid the risks of unstable foundations.
Moreover, the disaster highlighted the necessity of establishing emergency response plans. At the time of the incident, warnings were not issued in a timely manner, leaving hundreds of downstream residents with insufficient time to evacuate. The information and early warning systems in critical infrastructure were subsequently improved to minimize casualties in similar disasters.
Social and legal responsibilities have been emphasized following the incident. Many companies and local authorities have faced criticism for their lack of oversight, which led to a series of new safety standards being issued. This has also become a turning point, requiring engineers and contractors to take greater responsibility for ensuring the integrity of structures.
Memorial stone for the 7 families who lost their lives in the disaster. (Photo: Gettyimages).
Today, all that remains of the St. Francis Dam is a collection of massive concrete fragments scattered throughout the San Francisquito Canyon. This site has become a historical memorial, a reminder of the disaster that once occurred. In 2019, the area was designated as the St. Francis National Memorial and Monument, with the hope of preserving the memory of the victims and the lessons learned from this tragedy.
Plans to build a visitor center, museum, and memorial monuments are currently underway. A wall inscribed with the names of the victims is expected to be erected to honor those who lost their lives in the disaster.
The St. Francis Dam disaster is not just a tale of the collapse of a major structure but also a symbol of the mistakes made in ambition and management. It serves as a reminder that in every engineering project, caution and responsibility must always be prioritized. The lives lost can never be reclaimed, but the lessons from this event will forever guide future generations of engineers.
