Just before midnight on March 7, 1928, the St Francis Dam, located roughly 80km (50 miles) inland of Los Angeles, collapsed. There were no witnesses to the disaster – or none who survived – but investigators later determined that the 56-metre-tall (184ft-) barrier fell all at once, sending 12.4 billion gallons of water surging down the San Francisquito Canyon in a wave 43 metres (141ft) high.
Five hours later, the waters finally dumped into the Pacific Ocean, leaving chunks of concrete in their wake as heavy as 10,000 tonnes. By then, the gush of water was nearly 3km (2 miles) wide, laying waste to several towns along the way, cutting power throughout the region, and ultimately killing at least 431 people, many of whom were washed out to sea, their remains found as late as 1994 and as far as the Mexican border.
