The Great Chicago Fire
Three days, one fire, 300 people dead, 100,000 people
homeless, and 17,000 damaged structures.
On October 8, 1871, the heart of Chicago’s business district was
destroyed by a massive blaze that ravaged on for three days. The mostly
wooden architecture of the city at the time and the abundance of dry weather
made it a likely target for a fire. 
The fire started on the night of October 8th, supposedly by a cow who kicked over a lighted lantern in the O’Leary barn located at 137 DeKoven Street. Mrs. O’Learly denied the accusation, and it was never confirmed that that was the actual cause. Years later, in 1997, Chicago City Council exonerated Catherine O’Leary and her cow. After the fire initially started inside or near the barn it spread very rapidly towards the center of the city. It quickly reached the Court House, the Chicago Tribune headquarters, and even the Pumping Station making it very difficult for firefighters to try and save the city. Chicago was used to fires so they had buildings that were supposedly fireproof, like the Chicago Tribune place, but it was quickly realized that no building was safe. After causing $200 million in damages the blaze finally came to an end on October 10th after rain finally hit, giving the city and its firefighters some much needed relief. After the fire ended, martial law was put in place for several weeks because many people resorted to looting and lawbreaking since they lost everything. 
Reconstruction of the city started immediately making it even better than before. The architecture was modern and included the world’s first skyscraper. The city started to rewrite their building and fire standards, and soon had the country's most advanced fire fighting forces. Chicago’s population and economy grew very rapidly over the next couple of years. The population nearly doubled in 10 years, and by 1890 Chicago had the second largest population in the U.S. next to New York with 1 million people.
In 1956, the Chicago Fire Academy was built on the O’Leary property as a training site for Chicago Firefighters. Later, in October 2014, Redmood Theater in Chicago held The Great Chicago Fire Festival to celebrate the city’s prosperity after the fire, but they had some technical difficulties when fake houses failed to ignite properly. Despite the previous year’s mishaps they continued with the new tradition and had a very successful 2015 festival.
Sources:
http://www.history.com/topics/great-chicago-fire
https://en.wikipedia.org/wiki/Great_Chicago_Fire#Aftermath
http://www.greatchicagofire.org/great-conflagration
