Fort Dearborn was a United States fort built on the Chicago River in 1803 under John Whistler on the site of present-day Chicago. In 1810, when Whistler was recalled to Detroit, Michigan, he was succeeded by Captain Nathan Heald.

During the War of 1812, General William Hull ordered the evacuation of Fort Dearborn in August of 1812. Heald oversaw the evacuation, and on August 15, the evacuees were ambushed by about 500 Potawatomi Indians in the Fort Dearborn Massacre. The Potawatomi captured Heald and his wife, Rebekah, and ransomed them to the British. Of the 148 soldiers, women and children who evacuated the Fort, 86 were killed in the ambush. The Potawatomi burned the fort to the ground the next day.

Following the war, in 1816, a second Fort Dearborn was built. The fort consisted of a double wall of wooden palisade, officer and enlisted barracks, a garden, and other buildings. The Americans garrisoned the fort until 1823, when peace with the Indians led the garrison to be deemed redundant. This temporary abandonment lasted until 1828, when it was regarrisoned following the outbreak of war with the Winnebago Indians. Closed briefly before the Black Hawk War of 1832, in the early 1830s, part of the fort was demolished to make way for a new channel for the Chicago River. By 1837, the fort was being used by the Superintendent of Harbor Works.

In 1857, a fire destroyed nearly all the remaining buildings in the fort. The blockhouse and a few outbuildings were destroyed in the Great Chicago Fire of 1871.

In 1933, a stamp was issued in honor of the fort. Part of the fort outline is marked by plaques and a line embedded in the sidewalk and road near the Michigan Avenue Bridge and Wacker Drive. A few boards from the old Fort were retained, and they're now in the Chicago Historical Society in Lincoln Park.