The Debunker: Did Mrs. O'Leary's Cow Really Start the Great Chicago Fire?

by Ken Jennings

Did you know that September is National Preparedness Month? The catchy government slogan is "Be disaster aware! Take action to prepare!" But how disaster-aware are we really? Lots of the things we know about life's worst calamities are actually wrong--and in some cases, dangerously so. Luckily, Ken Jennings, Jeopardy! survivor and professional know-it-all, is here to set us straight. Because what could be more disastrous than ignorance? Well, maybe a big volcano. Ignorance, and also a big volcano.

The Debunker: Did Mrs. O'Leary's Cow Really Start the Great Chicago Fire?

On the night of October 8, 1871, a terrible fire laid waste to Chicago, at the time the fifth largest city in the nation. Nine square miles of the city were wiped off the map, leaving a third of the city's infrastructure down and over 100,000 Chicagoans homeless. The causes of the fire are easy to see in hindsight: a crowded city built almost entirely of wood, drought conditions, high winds to carry cinders aloft. But what set off the first spark?


The origin of the conflagration was traced to a barn at 137 DeKoven Street. In popular folklore, the blaze began when a cow owned by a Mrs. O'Leary kicked over a kerosene lamp, setting the building afire. The legend is so widespread that it's been depicted in a Normal Rockwell painting, a Brian Wilson song, countless Chicago-area parades, and the old Tyrone Power movie In Old Chicago. But all this Americana is, in fact, based on a journalistic hoax.

In 1893, the Chicago Tribune’s Michael Ahern admitted that he had invented the cow-and-lamp story out of thin air, to add color to his account of the fire. There were indeed five milk cows in the O'Leary barn that night, but the official investigation of the fire concluded that the fire most likely started with an accidental spark from a chimney, or some unknown human intervention. The bovine suspects weren't even mentioned. (Let's face it: none of them had much of a mooooo-tive.) But the anti-Irish sentiments of the time led Chicagoans to make much of the O'Learys' involvement: had they been drunk? Had they burned down their own barn and then hidden the evidence? Accusations followed Catherine O'Leary for the rest of her life, and her family said that she died heartbroken.

Quick Quiz: In 1998, the Chicago Fire won the championship in what sports league?

Ken Jennings is the author of six books, most recently his Junior Genius Guides, Because I Said So!, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at or on Twitter as @KenJennings.