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The Great Chicago Fire:
Did Mrs. O'Learys Cow

Really Cause It?



  • Arts & Humanities
    --Language Arts
  • Educational Technology
  • Social Studies
    ----U.S. History


  • 6-8
  • 9-12

Brief Description

Students think critically as they research/investigate facts about the Great Chicago Fire and come to a conclusion about its real cause. Was the fire really caused by Mrs. O’Leary’s cow?



  • research the Great Chicago Fire and theories about its origin.
  • think critically about who or what caused the fire.
  • write an essay with supporting information to explain their idea about the fire's cause.


fire, Chicago, Great Chicago Fire, fire safety, Fire Prevention Week

Materials Needed

  • computer access (in a classroom or computer lab)

Lesson Plan

One of the greatest disasters ever to strike the United States occurred in 1871. That year, a fire killed 300 people and left thousands homeless as it destroyed three square miles of Chicago. It was believed for many years that the fire -- which has come to be known as the Great Chicago Fire -- started when Mrs. O'Leary's cow kicked over a lantern in the barn. That theory appears to have had its origin in the October 9 issue of the Chicago Evening Journal, which reported that "the fire broke out on the corner of DeKoven and Twelfth streets, at about 9 o'clock on Sunday evening, being caused by a cow kicking over a lamp in a stable in which a woman was milking." Illustrations that accompanied that story or appeared soon after also painted Mrs. O'Leary as the cause. And a song made popular at the time


"One dark night, when we were all in bed,
Old lady Leary lit a lantern in the shed,
And when the cow kicked it over, it winked its eye and said,
There'll be a hot time in the old town tonight."

immortalized Mrs. O'Leary as the cause.

But, as it turns out, modern historians believe Mrs. O'Leary, a poor Irish immigrant, was simply a scapegoat. Historian Richard Bales has examined many pieces of evidence -- including county documents, land records, and transcripts of the investigation that followed the fire -- to make a solid case for Mrs. O'Leary's (and her cow's) innocence.

The activity that follows can be done in a computer lab or it could be set up in the one- or two-computer classroom as a learning center. Students can work on their own or in pairs to review the evidence presented with trial-lawyer precision by Richard Bales on his Web site, Did a Cow Really Cause the Great Chicago Fire? As students read the text, they might look for any suggestions about the actual cause of the fire:

  • Could Mrs. O'Leary or her cow have started the fire? What evidence suggests that was the case?
  • Could it have been Daniel "Peg Leg" Sullivan? Why might you think it was him?
  • Could it have been Dennis Regan? Why might you think it was him?
  • Could it have been Peg Leg Sullivan and Dennis Regan together? Why might you think that?
  • Could it have been a visitor to the McLaughlin house party that night? Why might you think that was the case?
  • Could the fire have been a total accident?


    A number of other interesting possibilities not covered in "Did the Cow Do It?" have been suggested. Those include that the firefighters were drunk that night and that a a comet could have triggered the fire.

    As students research, they will find much evidence that seems to exonerate Mrs. O'Leary. As the read, they should decide to do one of these two note-taking assignments:

  • List the five (5) pieces of evidence that you feel are the strongest ones in making a case for Mrs. O'Leary's innocence.
  • Record two (2) pieces of evidence that might point to any one of the other possible causes above.

    Then bring students together to share their thoughts. Do they come to any agreement as to 1) Mrs. O'Leary's innocence or 2) the real culprit?

    Finally, have students use their notes and the ideas shared during the discussion to write a one-page summary of who or what they think might have caused the Great Chicago Fire. Remind them that there is no right or wrong error, as nothing has ever been proven, but that their summaries will be graded based on the supporting evidence they provide for their ideas about who or what caused the fire.

    Additional Resources

    The Great Chicago Fire: The Web of Memory
    Essays and images from the Chicago Historical Society's collection.

    Great Chicago Fire
    Wikipedia online encyclopedia's account.

    Chicago Fire! [archived copy]
    National Geographic presents this account from the point of view of Claire Innes, a 12-year-old child at the time of the fire.

    The Great Chicago Fire
    A poem by Julia A. Moore.

    America's Story: The Great Chicago Fire
    See before- an after-the-fire illustrations of Chicago.

    Fire Prevention week is always celebrated the first full week in October. That week was chosen because it is the week in which the Great Chicago Fire took place.


    Assess students’ writing based on their use of supporting information -- information that supports their idea of who or what might have caused the Great Chicago Fire.

    Lesson Plan Source

    Submitted By

    Gary Hopkins


    National Standards 

    LANGUAGE ARTS: English
    GRADES K - 12
    NL-ENG.K-12.1 Reading for Perspective
    NL-ENG.K-12.2 Reading for Understanding
    NL-ENG.K-12.3 Evaluation Strategies
    NL-ENG.K-12.4 Communication Skills
    NL-ENG.K-12.5 Communication Strategies
    NL-ENG.K-12.8 Developing Research Skills
    NL-ENG.K-12.9 Multicultural Understanding
    NL-ENG.K-12.12 Applying Language Skills

    GRADES 5 - 12
    NSS-USH.5-12.6 Era 6: The Development of the Industrial United States (1870-1900)

    GRADES K - 12
    NT.K-12.1 Basic Operations and Concepts
    NT.K-12.5 Technology Research Tools

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    Originally published 09/28/2005
    Last updated 09/17/2010