Nearly 100 federal soldiers plus women and children were fleeing the fort. They thought they had a truce with the Potawatomi Indians for safe passage. The group only made it as far as what it is now 18th Street.
"They were attacked by the people who were supposed to be affording them their escort while they were in fact trying to leave the area," said Gillum Ferguson, author of "Illinois In The War of 1812".
On Wednesday, a simple ceremony honored all those who died on both sides.
"They were entering into Native American territory and that was a threat to Native Americans because they had an inherited right to this land," said Tracey Riedle.
The commemoration is not without a bit of controversy, starting with what to call what happened at Ft. Dearborn.
"They were under truce to retreat and I consider this a massacre, not a battle," said Edward Gordon, historian.
In recent years, though, other historians have begun to refer to it as "the Battle of Fort Dearborn."
Given the systematic scrubbing of Native Americans from the country in the years that followed, some see the gentler name as an acknowledgement of atrocities on both sides.
"Everyone in history likes to make it black and white, good guys against bad guys - but everything is much more complex, especially during this time," said Russell Lewis, Chicago History Museum.
The word "massacre" may be etched in stone on the Michigan Avenue Bridge House, but the history books continue to be written and revised.