The great San Francisco earthquake devastated the city

At 5:12 a.m. on April 18, 1906, the San Andreas fault tore open beneath Northern California, producing a magnitude-7.9 earthquake felt from Oregon to the Salinas Valley. The rupture stretched for hundreds of miles, but the worst was yet to come.

The shaking snapped gas lines and water mains across San Francisco, and the broken mains crippled firefighters just as dozens of blazes took hold. Over three days the fires consumed roughly 25,000 buildings across some 490 city blocks — by most estimates, the flames did the majority of the damage, not the quake itself.

Long cited as 700 deaths, the toll is now believed to be underestimated three- or fourfold, putting the dead above 3,000.

More than half the city’s residents were left homeless. The disaster reshaped building codes, insurance, and the young science of seismology for a century.