The earthquake struck while San Francisco slept. The ground shook violently for 45 to 60 seconds - an eternity for anyone experiencing it. Buildings swayed, facades crashed into streets, church bells rang by themselves. The ground itself rippled like waves on water.

The damage was immediate and catastrophic. City Hall, the pride of San Francisco, collapsed into rubble. The Valencia Street Hotel sank into the ground, killing most of its guests. Unreinforced brick buildings throughout the city crumbled. The waterfront, built on filled land, liquefied. But survivors picking themselves up from the wreckage didn't yet know the worst was coming.

The earthquake had broken gas mains throughout the city. Small fires broke out immediately - from overturned stoves, from exposed flames, from sparking electrical wires. Under normal circumstances, the fire department could have contained them. But the earthquake had also broken the water mains.

Firefighters connected hoses to hydrants and got nothing. The city's water distribution system was shattered. Fire Chief Dennis Sullivan had been mortally wounded when a chimney crashed through his fire station. Leaderless and without water, the fire department watched helplessly as dozens of small fires merged into an inferno that would burn for three days.

The fires burned out of control through the commercial district, the residential neighborhoods, Chinatown, and the waterfront. The Army dynamited buildings to create firebreaks, but the explosions often spread the fire instead of stopping it. Soldiers shot suspected looters on sight. Refugees fled ahead of the flames, carrying whatever they could save.

The fire created its own weather - a firestorm that generated winds that drove the flames forward. Temperatures reached over 2,000 degrees. Stone and brick glowed red before crumbling. The fire jumped wide streets and consumed entire city blocks in minutes. At night, the glow could be seen from 50 miles away.

A quarter of a million people - over half the city's population - were suddenly homeless. They fled to Golden Gate Park, the Presidio, the beaches, anywhere the fire couldn't reach. Tent cities sprang up overnight. The Army distributed food and supplies. Relief poured in from around the world.

The refugee camps would exist for over two years. Some residents never returned. The Chinese community, whose neighborhood had been completely destroyed, faced discrimination when trying to rebuild. Insurance companies refused to pay claims, arguing that fire damage wasn't covered by earthquake policies. The disaster exposed and exacerbated the inequalities of early 20th-century America.

San Francisco rebuilt with remarkable speed. Within three years, the city had reconstructed most of what had burned. New buildings were designed with fire safety in mind. A new water system included a dedicated high-pressure firefighting supply. The city that emerged was different - newer, more planned, but still unmistakably San Francisco.

The 1906 earthquake also transformed earthquake science. The study of the San Andreas Fault began in earnest. Seismology became a serious discipline. Building codes were developed that would eventually save thousands of lives in future earthquakes. The disaster that killed 3,000 people taught lessons that protect millions today.