"One dark night, when people were in bed,

Mrs. O' Leary lit a lantern in her shed,

The cow kicked it over, winked its eye, and said,

There'll be a hot time in the old town tonight."

What do we know about the Great Chicago Fire?

Historians agree that on Sunday evening, October 8, 1871, the Chicago Fire did indeed start in the barn of Mr. and Mrs. Patrick and Catherine O'Leary. While the blaze ironically spared the O'Leary home, located on the city's West Side at 137 De Koven Street, much of the rest of Chicago was not so fortunate. Before the fire died out in the early morning of Tuesday, October 10, it had cut a swath through Chicago approximately three and one-third square miles in size. Property valued at $192,000,000 was destroyed, 100,000 people were left homeless, and 300 people lost their lives.

In November and December of 1871 the Board of Police and Fire Commissioners held an inquiry. The purpose of this investigation was to determine, among other things, the cause of the fire. The board interviewed fifty people, including Mr. and Mrs. O'Leary. A shorthand reporter took down over 1100 pages of handwritten testimony. Despite all this, the board members failed to ascertain the fire's cause, stating merely in their report that "whether it originated from a spark blown from a chimney on that windy night, or was set on fire by human agency, we are unable to determine."

So did Mrs. O'Leary and her cow cause the fire, or is this merely a nineteenth-century urban legend? An analysis of the original transcripts of this inquiry, 1871 Chicago real estate records, and other period source materials provide powerful evidence that the latter may be the case. Furthermore, these same records provide a fascinating theory as to who really did cause the fire.

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