April 18 is the 100th anniverary of the earthquake that hit San Francisco in 1906. The SFGate website looks back at life before the quake, the disaster, and the aftermath:
The Great Quake 1906-2006

The Virtual Museum of the City of San Francisco offers a timeline, news clippings, eyewitness accounts, and more:
The Great 1906 Earthquake and Fire

More information and photos from the U.S. Geological Survey:
The Great 1906 San Francisco Earthquake

Further reading: Books About the San Francisco Earthquake