Although there had been treaties and seemingly cordial trading between the Native Americans and the new settlers in that area, recent fighting in nearby areas like the Battle of Tippecanoe less than a year earlier kept all sides on edge, and the British aim to maintain a barrier between America and Canada by propping up Native American tribes led to a controversial battle in the Illinois Territory at Fort Dearborn, a fort built along the Chicago River, shortly after the War of 1812 broke out. When the war came, the close proximity of British forces compelled American military officers in the area to attempt to evacuate the garrison at Fort Dearborn, but misunderstandings and a lack of time resulted in Potawatomi warriors ambushing the soldiers and several civilians before they could retreat back to Fort Wayne, Indiana. In the wake of cutting down dozens of whites, the Potawatomi laid waste to Fort Dearborn itself, and though the fighting was technically a battle, in America the Battle of Fort Dearborn was known colloquially as the Fort Dearborn Massacre.

Though it started as a 300 person settlement in 1832, Chicago's location near the Great Lakes and its access to the Mississippi River turned it into a major trading city overnight. The city became even more important when railroads were constructed to connect the country, making it the first major city in the "West" during the mid-19th century. By 1871, the original 300 person settlement was now home to about 300,000 people, and Chicago had become the first major city built by Americans rather than European colonial powers