On April 18, 1906, the deadliest earthquake in U.S. history struck San Francisco, killing over 3,000 people. The quake, which was estimated to have reached as high as 8.3 magnitude on the Richter scale, was followed by raging fires across the city. Major earthquakes in California have occurred frequently, including the Fort Tejon/Kearn County blast in 1857 and the recent Ridgecrest earthquake on July 4.