Heald over saw the evacuation of the fort in August of 1812 during the War of 1812. On August 15, he and his wife, Rebekah, were captured by the Potawatomi Indians during the Fort Dearborn Massacre and were ransomed to the British. Of the 148 soldiers, women and children who evacuated the Fort, 86 were killed in the ambush. Following the massacre, the Potawatomi burned the fort to the ground.
Following the war, in 1816, a second Fort Dearborn was built. The Americans garrisoned the fort until 1823, when peace with the Indians led to a feeling that the garrison was 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.