Determining the Location of the 22 May 1855 Chicago Area Tornado.

The number and location of tornadoes in the greater Chicago area is a topic of frequent interest among the media, public, and local government agencies served by the National Weather Service (NWS) Chicago Forecast Office. While accounts of tornadoes over the last several decades are generally clear, tornadoes occurring prior to 1950—especially those considered to be weak—are often more difficult to discern owing to limited corresponding detailed reports. As part of an effort to review and update all tornadoes known to have occurred within the modern-day boundaries of Chicago, NWS Chicago staff reviewed the 22 May 1855 tornado, which is regarded as the first to impact the city of Chicago. Multiple sources reported that the tornado occurred near the town of Jefferson, which eventually became the Jefferson Park neighborhood of Chicago. However, after reviewing multiple historical records, newspaper articles, property maps, and genealogical information, the actual location of the tornado was determined to have been in present-day Des Plaines. Confusion over the name "Jefferson" likely led to the misunderstanding that, until now, has been perpetuated through numerous reports and media accounts. [ABSTRACT FROM AUTHOR]