The Chicago Fire of 1871, commonly referred to as the Great Chicago Fire, began sometime in the evening on October 8, 1871. It was started in or around a barn owned by Catherine and Patrick O'Leary, located at 137 DeKoven Street on the southwest side of the city. Dry seasonal conditions, coupled with the extensive use of wood for building construction in the city in the late 19th century, caused the blaze to expand quickly.
After its initial ignition, the Great Chicago Fire quickly spread north and east towards the center of the city, largely due to strong southwesterly winds. An early routing error sent some of Chicago's 185 firemen to the wrong location, allowing the blaze to grow unchecked. The wind was sufficient to carry embers and burning material across the South Branch of the Chicago River, igniting lumber yards and warehouses along its length and into the central business district. The destruction of the city's main waterworks prevented the fire department from being able to adequately fight the blaze.
Rain on October 9th ultimately extinguished the fire, which burned a 3.3-square mile area and killed 300 people. The disaster, historically one of the worst in 19th century America, caused approximately $200 million in damage and left 100,000 residents homeless.