On April 18, 1906, an earthquake struck near San Francisco, California, United States, then the largest city on the West Coast. The earthquake occurred offshore, at an outcropping called Mussel Rock, a little after 5:00 a.m.

Tremors were felt from the state of Oregon to Los Angeles, California, and inland toward the state of Nevada. The exact magnitude of the earthquake is disputed, but the most common estimate is about 7.9—a very damaging temblor. Fires immediately broke out in San Francisco due to broken gas lines, fallen power lines, and lanterns that had toppled over during the earthquake. Water lines were ruptured as well, which made it difficult to put the fires out.

It is estimated that 3,000 people were killed during the earthquake and its aftershocks, which lasted for days. The earthquake displaced even more people from their homes.

The earthquake occurred as a result of a shift along the San Andreas Fault, which bisects the San Francisco Peninsula just to the west of the city. The land on the eastern side of the fault, including the city and San Francisco Bay, moved southward, while the land on the western side was pushed northward. More than six meters (20 feet) of displacement occurred during the quake.