On April 18, 1906, at 5:12 AM, a magnitude 7.9 earthquake struck the coast of Northern California, producing extreme shaking (Intensity XI) that was felt from Eureka to the Salinas Valley. The quake, triggered by the San Andreas Fault—a transform boundary between the Pacific and North American plates—ruptured a 296-mile segment, with a foreshock about 20 seconds before the main shock, which lasted 42 seconds. The disaster ignited massive fires that raged for days, killing over 3,000 people and destroying more than 80% of San Francisco, making it the deadliest earthquake in U.S. history and California's worst natural disaster. While the epicenter was long thought to be near Olema, modern research, including a 2019 study, now places it offshore near San Francisco, supported by tsunami records and refined triangulation data. The rupture propagated both north and south at speeds exceeding seismic S-waves (supershear), with ground displacements up to 28 feet, and shaking felt as far away as Oregon, Los Angeles, and central Nevada. This catastrophic event remains a key benchmark for understanding strike-slip faulting and seismic risk in California.