The Great Chicago Fire was a conflagration that burned in the American city of Chicago during October 8–10, 1871. The fire killed approximately 300 people, destroyed roughly 3.3 square miles (9 km2) of the city including over 17,000 structures, and left more than 100,000 residents homeless. The fire began in a neighborhood southwest of the city center. A long period of hot, dry, windy conditions, and the wooden construction prevalent in the city, led to the conflagration. The fire leapt the south branch of the Chicago River and destroyed much of central Chicago and then leapt the main stem of the river, consuming the Near North Side.

Chicago is the most populous city in the U.S. state of Illinois and in the Midwestern United States. With a population of 2,746,388 in the 2020 census, it is the third-most populous city in the United States after New York City and Los Angeles. As the seat of Cook County, the second-most populous county in the U.S., Chicago is the center of the Chicago metropolitan area, often colloquially called "Chicagoland" and home to 9.6 million residents.