he Great Chicago Fire is perhaps the most well-known disaster in Chicago's history. Beginning around 9 pm on October 8, 1871, in the O'Leary's barn, the fire burned almost four square miles of Chicago's business district. The cause is still not known, although Mrs. O'Leary and her cow are often blamed. However the fire started, this disaster killed hundreds, destroyed millions of dollars worth in property, and left thousands homeless. From the smoldering ashes, the citizens of Chicago began to rebuild and a new era of building began in the city's history. The new building spurt made Chicago one of the most populous, most economically profitable, and most modern cities in the United States. The Great Chicago Fire caused huge tragedy, but out of the ashes arose the modern Chicago metropolis.