The Great Chicago Fire was a conflagration that burned for more than two days and destroyed about four square miles of the city. It killed hundreds of people, left 90,000 homeless, and destroyed some $200 million worth of property. Originally composed of mostly wooden structures, the city was rebuilt with stone and steel and became a center of industry. According to early accounts of the disaster, the blaze began in a barn owned by Patrick and Catherine O’Leary. What supposedly caused the fire? Discuss