OCTOBER 8, 1871: A fire ignited in a barn on Chicago’s west side grows into a massive conflagration, destroying more than four square miles of the city, incinerating 17,000 buildings and killing some 300 people and leaving another 100,000 homeless. Smaller blazes were a frequent problem in the poorer neighborhoods of the rapidly-growing city, where wooden structures were more common, and emergency crews had fought another major fire the previous night, exhausting firemen and damaging equipment. The fire raged for two days before rain and firebreaks created by undeveloped land halted its advance. According to popular legend a cow owned by the O’Learys started the blaze, but in 1997 the city council officially exonerated the infamous bovine.