What really happened in Mrs. O'Leary's barn that autumn night in Chicago? Though no one knows for sure, what is certain is someone, or something, started a load of hay on fire, and the city of Chicago would never be the same. The Great Chicago Fire of 1871 raged for more than 24 hours, obliterating the downtown and sparking a mass exodus to the prairies and lake. The flames grew so hot that they melted iron and marble, and the twisting winds tore the roofs off houses. The individual stories of courage and tragedy, recounted by survivors who fought for their lives, captivated a nation and elicited an outpouring of aid. The stricken city would rise again, but its tale of near extinction would remain one of America's most defining legends.