Title: 1868 Hayward earthquake
Content:  The 1868 Hayward earthquake occurred in the San Francisco Bay Area, California, United States on October 21. With an estimated moment magnitude of 6.3–6.7 and a maximum Mercalli intensity of IX (Violent), it was the most recent large earthquake to occur on the Hayward Fault Zone. It caused significant damage and a number of deaths throughout the region, and was known as the "Great San Francisco earthquake" prior to the 1906 San Francisco earthquake and fire.
Title: 1906 San Francisco earthquake
Content:  The 1906 San Francisco earthquake struck the coast of Northern California at 5:12 a.m. on Wednesday, April 18, with an estimated moment magnitude of 7.9 and a maximum Mercalli intensity of XI (Extreme). High-intensity shaking was felt from Eureka on the North Coast to the Salinas Valley, an agricultural region to the south of the San Francisco Bay Area. Devastating fires soon broke out in the city and lasted for several days. More than 3,000 people died, and over 80% of the city of San Francisco was destroyed. The events are remembered as one of the worst and deadliest earthquakes in the history of the United States. The death toll remains the greatest loss of life from a natural disaster in California's history and high on the lists of American disasters.
Title: George Pardee
Content:  In the early morning hours of April 18, 1906, a magnitude 7.7 to 8.3 earthquake struck along the San Andreas Fault, with an epicenter two miles (three km) from San Francisco, near Mussel Rock in neighboring San Mateo County. While cities as spread as Santa Rosa, San Jose and Palo Alto suffered considerable damage, San Francisco remained hardest hit, with resulting fires destroying much of the central core of the city. As telegraphed reports slowly filtered into the Governor's Office in Sacramento, Pardee mobilized the California Army National Guard to be dispatched to San Francisco, though Pardee was unaware that federal troops of the 
Title: History of San Francisco
Content:  On April 18, 1906, a devastating earthquake resulted from the rupture of over 270 miles of the San Andreas Fault, from San Juan Bautista to Eureka, centered immediately offshore of San Francisco. The quake is estimated by the USGS to have had a magnitude of 7.8 on the Richter scale. Water mains ruptured throughout San Francisco, and the fires that followed burned out of control for days, destroying approximately 80% of the city, including almost all of the downtown core. Many residents were trapped between the water on three sides and the approaching fire, and a mass evacuation across the Bay saved thousands. Refugee camps were also set up in Golden Gate Park, Ocean Beach, and other undeveloped sections of the city. The official death toll at the time was 478, although it was officially revised in 2005 to 3,000+. The initial low death toll was concocted by civic, state, and federal officials who felt that reporting the actual numbers would hurt rebuilding and redevelopment efforts, as well as city and national morale. The death toll from this event had the highest number of deaths from a natural disaster in California history.
Title: History of San Francisco
Content:  On October 17, 1989, an earthquake measuring 6.9 on the moment magnitude scale struck on the San Andreas Fault near Loma Prieta Peak in the Santa Cruz mountains, approximately 70 miles (113 km) south of San Francisco, a few minutes before Game 3 of the 1989 World Series was scheduled to begin at Candlestick Park. The quake severely damaged many of the city's freeways including the Embarcadero Freeway and the Central Freeway. Mayor Agnos made the controversial decision to tear down the Embarcadero Freeway, opening the waterfront but eventually shifting Chinatown voters away from him and costing him re-election in 1991. The quake also caused extensive damage in the Marina District and the South of Market neighborhoods.
Title: San Francisco
Content:  at the time. Around 1901, San Francisco was a major city known for its flamboyant style, stately hotels, ostentatious mansions on Nob Hill, and a thriving arts scene. The first North American plague epidemic was the San Francisco plague of 1900–1904. At 5:12 am on April 18, 1906, a major earthquake struck San Francisco and northern California. As buildings collapsed from the shaking, ruptured gas lines ignited fires that spread across the city and burned out of control for several days. With water mains out of service, the Presidio Artillery Corps attempted to contain the inferno by dynamiting blocks of buildings 
Title: Timeline of the San Francisco Bay Area
Content:  building pictured) ; Hill Park is established in San Francisco An earthquake estimated at 6.3–6.7 on the moment magnitude scale hits the Bay Area, with an epicenter in the East Bay. It causes significant damage throughout the region, and comes to be known as the "Great San Francisco earthquake". (damage in the Haywards area pictured, right) The Convent of Our Lady of the Sacred Heart (pictured, right) in Oakland is established by members of the Sisters of the Holy Names from Canada The University of California (logo pictured, left) is established in Berkeley, along with the first campus in the 
Title: 1957 San Francisco earthquake
Content:  The 1957 San Francisco earthquake (also known as the Daly City earthquake of 1957) occurred on March 22 at 11:44:22 local time with a moment magnitude of 5.7 and a maximum Mercalli Intensity of VII (Very strong). It was located just off the San Francisco Peninsula near the San Andreas Fault and was felt in a limited portion of Northern and Central California. There was a non-destructive foreshock and aftershock sequence that lasted for several months. With financial losses of around US$1 million, damage was considered minimal, with one death and forty injuries.
Title: San Andreas Fault
Content:  of San Francisco and Daly City. ; 1989 Loma Prieta earthquake: About 40 km were ruptured (although the rupture did not reach the surface) near Santa Cruz, California, causing 63 deaths and moderate damage in certain vulnerable locations in the San Francisco Bay Area. Moment magnitude was about 6.9. This quake occurred on October 17, 1989, at approximately 5:04 pm PDT. ; 2004 Parkfield earthquake: On September 28, 2004, at 10:15 a.m. PDT, a magnitude 6.0 earthquake struck the Parkfield area. It was felt across the state, including the San Francisco Bay Area. The San Andreas Fault has had some notable earthquakes in historic times: 
Title: 1906 in science
Content: April 18 – The San Francisco earthquake, an estimated 7.9 on the Richter scale and centered on the San Andreas fault, strikes near San Francisco, California. The earthquake and fire destroy over 80% of the buildings in the city, and kill as many as 6,000 people. Harry Fielding Reid devises the elastic-rebound theory to account for earthquake mechanism. ; Richard Oldham argues that the Earth has a molten interior. 

Question: when did the big earthquake hit san francisco?
Answer: 1906 San Francisco earthquake.