The Great Chicago Fire (pictured), began and proceeded to destroy much of the city's central business district, killing 300 people and leaving 90,000 others homeless.

The Great Chicago Fire was a conflagration that burned in the American city of Chicago, Illinois during October 8–10, 1871. The fire killed approximately 300 people, destroyed roughly 3.3 square miles (9 km²) of the city including over 17,000 structures, and left more than 100,000 residents homeless. The fire began in a neighborhood southwest of the city center. A long period of hot, dry, windy conditions, and the wooden construction prevalent in the city, led to the conflagration spreading quickly. The fire leapt the south branch of the Chicago River and destroyed much of central Chicago and then crossed the main stem of the river, consuming the Near North Side.

A central business district (CBD) is the commercial and business center of a city. It contains commercial space and offices, and in larger cities will often be described as a financial district. Geographically, it often coincides with the "city centre" or "downtown". However, these concepts are not necessarily synonymous: many cities have a central business district located away from its traditional city center, and there may be multiple CBDs within a single urban area. The CBD will often be highly accessible and have a large variety and concentration of specialised goods and services compared to other parts of the city. Midtown Manhattan is the world's largest central business district. In the City of London, the largest concentration of economic output in the world is held there, with many headquarters of major financial and law firms being based in the City.