Fort Dearborn was a United States fort built in 1803 beside the Chicago River in what is now Chicago, Illinois. It was constructed by troops under Captain John Whistler and named in honor of Henry Dearborn, then United States Secretary of War. The original fort was destroyed following the Battle of Fort Dearborn in 1812, and a new fort was constructed on the same site in 1816. The fort was de-commissioned by 1837, and parts of the fort were lost to the widening of the Chicago River in 1855 and a fire in 1857; the last vestiges being destroyed in the Great Chicago Fire of 1871. The site of the fort is now a Chicago Landmark, part of the Michigan–Wacker Historic District.