The 1906 San Francisco earthquake (wiki) struck the coast of Northern California at 5:12 a.m. on April 18 with an estimated"moment magnitude" of 7.8 and a maximum "Mercalli intensity" of "XI" ("Extreme"). Severe 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. As a result, about 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 natural disasters 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 in the lists of American urban disasters.
Here's the same area of Market Street after April 18 earthquake:
And a side by side comparison of the two trips:
Library of Congress (silent) footage of the quake itself:
And, lastly, a recent documentary on the disaster:
Want more? Check out Google images of the earthquake.