before the fire, while strong southwest winds helped to carry flying embers toward the heart of the city. In 1871, the Chicago Fire Department had 185 firefighters with just 17 horse-drawn steam pumpers to protect the entire city. The initial response by the fire department was timely, but due to an error by the watchman, Matthias Schaffer, the firefighters were initially sent to the wrong place, allowing the fire to grow unchecked. An alarm sent from the area near the fire also failed to register at the courthouse where the fire watchmen were, while the firefighters were tired from having fought numerous small fires and one large fire in the week before. These factors combined to turn a small barn fire into a conflagration. Spread When firefighters finally arrived at DeKoven Street, the fire had grown and spread to neighboring buildings and was progressing toward the central business district. Firefighters had hoped that the South Branch of the Chicago River and an area that had previously thoroughly burned would act as a natural firebreak. All along the river, however, were lumber yards, warehouses, and coal yards, and barges and numerous bridges across the river. As the fire grew, the southwest wind intensified and became superheated, causing structures to catch fire from the heat and from burning debris blown by the wind. Around midnight, flaming debris blew across the river and landed on roofs and the South Side Gas Works. With the fire across the river and moving rapidly toward the heart of the city, panic set in. About this time, Mayor Roswell B. Mason sent messages to nearby towns asking for help. When the courthouse caught fire, he ordered the building to be evacuated and the prisoners jailed in the basement to be released. At 2:30 a.m. on the 9th, the cupola of the courthouse collapsed, sending the great bell crashing down. Some witnesses reported hearing the sound from a mile (1.6 km) away. As more buildings succumbed to the flames, a major contributing factor to the fire's spread was a meteorological phenomenon known as a fire whirl. As overheated air rises, it comes into contact with cooler air and begins to spin, creating a tornado-like effect. These fire whirls are likely what drove flaming debris so high and so far. Such debris was blown across the main branch of the Chicago River to a railroad car carrying kerosene. The