Early in the morning of Wednesday, April 18, 1906, the San Francisco area was shaken by a massive earthquake. Over the course of the next four days, fires spread through large swaths of the city, started by broken gas lines, fallen electrical wiring, and damaged chimneys. Broken water mains prevented the fire department from effectively battling the blazes. By the time the fires were finally extinguished on the afternoon of Saturday, April 21, nearly 3000 people were dead and 500 city blocks destroyed. Before the year was over, the Edward Hilton Company of San Francisco had collected and sifted through the available information to publish this concise and lucid analysis of what had happened.