On this date in 1871, what became known as the Great Chicago Fire began and would last till 10 October. The fire began around 9 pm on October 6 possibly at a barn owned by the O’leary family or in the nearby area southwest of city center. It consumed a shed on that farm and then spread outward. Due to a period of hot, dry and windy conditions, the fire would spread rapidly. With homes and buildings built mostly of wood, it also provided fuel for the fire as well.
The fire leapt the south branch of the Chicago River destroying central Chicago. It leapt across the main river branch and consumed the north side as well. 300 people were killed and a large swath of the city (about 3.3 square miles) was destroyed. 100,000 people were left homeless because of the fire. After the fire help poured in from all over the country and internationally as well. Money from Great Britain helped build the Chicago Public Library that would be free to everyone.
The aftermath brought reconsideration of many things particularly in the area of building construction. Fire prevention became a big topic and construction of brick rather than wood buildings would result. With the right infrastructure in place, it would prevent such a catastrophe from happening again. Rebuilding began right away with higher standards and sometimes with buildings that were considered better than the ones that burned down.
History.com, Great Chicago Fire