Back then in the 19th century, Chicago was a rapidly growing city. Immigrants from all over the world had come to America in hopes for a better life. Due to the rapidly growing population, the city was forced to build many buildings in a short amount of time. Naturally, the city would use the cheapest material which at the time was lumber. Buildings were all in close proximity and were haphazardly thrown together. Due to the drought that Chicago was experiencing, The wood became very dry and flammable.
Ellis island was built in 1892 due to the outbreak in Immigration.
At the time, the Chicago Fire Department (CFD) were said to have state of the art fire defense. Some examples would be Street call boxes which were similar to our fire alarms. They also had horse drawn steam engines which are like our firetrucks. Despite having the state of the art defenses, the CFD were still short on members and equipment. They only had 185 full time firefighters. They needed fire boats along the Chicago river which was lined with coal factories and lumberyards. They also needed Inspectors to check the carelessly built building. Unfortunately, this was all shot down by the Business Committee because it was thought to be to costly.
The fire started on October 8, 1871 9pm and ended roughly 30 hours later on October 10. It had been an unusually dry summer (Four months) in the city of Chicago which made the fire spread easier. The fire had started at the O'Leary's barn but the reason is still unknown. There are many theories on how the fire started but the most common urban legend states that the O'Leary's cow had accidentally kicked down a kerosene lamp which lit a stack of hay on fire.