A fire at the Iroquois Theater in Chicago, Illinois kills at least 605.

The Iroquois Theatre fire was a catastrophic building fire in Chicago, Illinois, that broke out on December 30, 1903, during a performance attended by 1,700 people. The fire caused 602 deaths and 250 non-fatal injuries. It ranks as the worst theater fire in the United States, surpassing the carnage of the Brooklyn Theatre fire of 1876, which claimed at least 278 lives.

Chicago is the most populous city in the U.S. state of Illinois and in the Midwestern United States. Located on the western shore of Lake Michigan, it is the third-most populous city in the United States with a population of 2.74 million at the 2020 census, while the Chicago metropolitan area has 9.41 million residents and is the third-largest metropolitan area in the nation. Chicago is the seat of Cook County, the second-most populous county in the United States.