In 1803, Thomas Jefferson bought a massive parcel of land from Napoleon Bonaparte that stretched from New Orleans to what is now the northwestern tip of Montana. While the Louisiana Purchase didn’t include the land that is now Chicago, it made the trade routes through the area—specifically the intersection of the Chicago River and Lake Michigan—significantly more important to the expanding United States.
To protect the area, the army built a fort on the south side of the intersection, across from the cabin of Chicago settler Jean Baptiste Pointe DuSable (who was once described to me by a well-meaning Chicago Historical Society docent as “an African-American from Haiti”). The army named its new fortress Fort Dearborn in honor of U.S. Secretary of War Henry Dearborn.
The fort endured as a vital military garrison until August 1812, when it was burned to the ground by the Potawatomi Indians in the aptly named War of 1812.
A second Fort Dearborn was built on the site in 1816. It survived eras of peace and conflict with a number of other tribes until part of it was demolished to make way for a new Chicago River channel in 1832. The rest of the fort was destroyed by a fire in 1857, and the few surviving outbuildings were leveled by the Great Chicago Fire in 1871.
Today, all that’s left of the fort are the outlines of its footprint, marked by plaques embedded in the sidewalk where Wacker Drive meets Michigan Avenue:
Here’s what the site looks like today. I took this picture facing north, where Michigan Avenue starts being called “The Magnificent Mile” (but only in marketing materials—I’ve never heard a real person use that term in general conversation).