Did a Cow Really Cause the Great Chicago Fire of 1871?

For decades, many believed the origin of the Great Chicago Fire of 1871 was an ill-tempered cow kicking over a lantern. An insurance map of the fire’s path suggested otherwise.
A map of the Great Chicago Fire of 1871 showing where the fire burned.
A map of the Great Chicago Fire of 1871 showing where the fire burned. / Library of Congress, Geography and Map Division // Public Domain

Around 9 p.m. on Sunday, October 8, 1871, a fire started in a barn in the alley behind 137 DeKoven Street in Chicago. Two days later the blaze died out, after burning nearly 3.3 square miles of the city. The Great Chicago Fire killed 300 people, left some 100,000 residents without homes, and destroyed $200 million in property.

In all of American history, no bovine is more infamous than the cow belonging to Patrick and Catherine O’Leary accused of starting what fire marshal Robert A. Williams called a “hurricane of fire and cinders.” Even as the fire cut a swath through the city, neighbors and newspaper reporters quickly placed the blame on the O’Learys and their cow. In the early hours of October 9, newspapers first reported that the blaze started when the cow kicked over a kerosene lantern while Catherine was milking the animal.

After the fire was put out, the story evolved and more blame fell on the O’Learys. Some papers reported that Mrs. O’Leary had been selling the cow’s milk illegally, and when city officials discovered her side hustle, they cut her off. The fire, it was implied, was an act of revenge.

Other newspapers maintained that the fire was an accident, and that a lantern had simply been knocked over, either by the cow or by Mrs. O’Leary.

A lithograph of the Great Chicago Fire of 1871.
A lithograph of the Great Chicago Fire of 1871. / Currier & Ives, Wikimedia Commons // Public Domain

That November, the Board of Police and Fire Commissioners started an inquiry into the fire’s cause and the city’s response. In interviews with the board, Mrs. O’Leary testified that she never milked the cows in the evening and that she was asleep when the fire started, having gone to bed early complaining of a sore foot. Daniel “Pegleg” Sullivan, a neighbor who was the first person to raise the alarm about the fire, also testified and confirmed Catherine’s alibi. After two months and 1100 pages of handwritten testimony, the board members couldn’t say much about the origin of the fire, except that it started in the barn. “Whether it originated from a spark blown from a chimney on that windy night or was set on fire by human agency,” they wrote, “we are unable to determine."

But the damage to Catherine O’Leary and her cow was done. The story of the cow and the lantern circulated quickly and widely and took hold in the public imagination. Mrs. O'Leary lived out the rest of her life as a recluse, reportedly only leaving her home to attend mass. Every October, reporters came to her looking for a quote for their fire anniversary stories and she shooed them away, invoking the name of her son James, who grew up to be a gambling boss known as “Big Jim” O'Leary.

“I know bad people,” she’d say, as she showed the men the door. She died in 1895. Her obituary and death certificate listed the cause as acute pneumonia, but neighbors and friends said the real cause was a “broken heart” from the unfounded blame she received.

Then, a century after her death, Catherine O’Leary and her cow were cleared of any wrongdoing—and another suspect was discovered.

A Map of the Great Chicago Fire Offers Clues

Richard Bales, an assistant regional counsel with the Chicago Title Insurance Company, became interested in the Great Chicago Fire when he wrote a paper about it for a college course. His company maintains the only set of land records that survived the Great Fire of 1871, and he used them to dig further into the legend of the O’Learys’ cow and the origin of the fire. In 1997, he published an article, and later a book, on his research.

Bales discovered that the fire probably wasn’t intentionally set. The O’Learys’ barn was full of animals, some of which belonged to neighbors and some that were used for Catherine’s milk business. There were five cows, a calf, and a horse. There was also a new wagon nearby in the alley, and none of the property or real estate was insured. “Had [Catherine] been in the barn when the fire broke out, it seems unlikely that she would have run back into her home and allowed her property to both literally and figuratively go up in smoke,” Bales wrote. “Instead, she would have cried for help and attempted to extinguish what was then just a minor barn fire and save the building and its contents.”

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As for the cow, several reporters came forward decades after the Great Chicago Fire to admit that the story of the cow kicking the lantern was a fabrication, or at least came from unreliable sources. Reporter Michael Ahern, who was working for the Chicago Republican in 1871, admitted in a Chicago Tribune column in 1921 that he and two colleagues made up the cow story to add color to their copy. After that, another reporter, John Kelley, wrote to the O’Learys’ grandson saying that he had written the first iteration of the cow story under Ahern’s byline, since his colleague was too drunk to file the piece.

Meanwhile, the Chicago Daily Journal explained that on the night of the fire, one of its reporters had gone to the O’Learys' neighborhood and heard the cow story from residents there, and the paper ran with it without further confirmation. Recollections of the Great Chicago Fire of 1871 published by one of the O’Learys’ neighbors alleged that some neighborhood kids who hadn’t been anywhere near the barn spent the night telling anyone who would listen about a cow kicking a lantern.

The Real Origin of the Great Chicago Fire of 1871

Bales suspected that the fire was started by “Pegleg” Sullivan, the man who first noticed it. When he testified before the investigative board, Sullivan said that he visited the O’Leary house around 8 p.m. and found Catherine in bed and Patrick ready to join her. He headed home, but then kept going past his house and stopped in front of a neighbor’s house to smoke a pipe. He looked up and saw fire coming from the O’Learys' barn and ran into it to try to extinguish the flames and free the animals before seeking help.

After mapping the various homes and properties, Bales doubted Sullivan’s version of the events. The buildings were arranged in such a way that, from where he stood to smoke his pipe, Sullivan would not have been able to see the barn because another home would have blocked his view. What’s more, Bales wrote, Sullivan had a wooden leg—as one might guess from his nickname—and couldn’t move very fast. Yet, Sullivan claimed that he ran from his smoking spot to the barn, a distance about half the length of a football field; escaped the barn before the fire consumed it, and then ran to alert the O’Learys and the authorities. Given his mobility issue, the distances involved, and the speed with which the fire spread, Bales argued that Sullivan could not have done these acts without being injured by the fire.

Cleanup at Clark And Madison Streets After Chicago Fire, IL, 1871.
Chicagoans begin the cleanup at Clark and Madison streets after the Great Chicago Fire of 1871. / Hulton Archive/GettyImages

There’s also the question of why Sullivan walked past his own house to smoke his pipe in front of his neighbor’s house. Bales suggested that was part of Sullivan’s alibi. Claiming to smoke his pipe where he did put him outside and close enough to the barn that he could claim to have seen the fire, but out of view of his neighbors, the McLaughlins, who were having a party that night and would have been able to see him if he was standing in front of his own house.

Bales argued that Sullivan was in or around the barn that night—his mother kept one of her cows there and he may have gone to feed it. By accident, with a careless flick of a match or a stray ember from his pipe or by bumping a lantern, Sullivan started the fire. And when he realized he couldn’t put the fire out on his own, he ran for help and came up with a cover story to escape blame.

In 1997, convinced by Bales’s argument and the evidence, the Chicago City Council passed an ordinance exonerating Mrs. O’Leary and her cow.

A version of this story was published in 2014; it has been updated for 2024.