During the American War of Independence (1776-1783), the British reoccupied Fort Cumberland. Other additions were made to the fort over the years, including new barracks in 1778. Repairs were carried out in 1783 and dilapidated buildings were demolished. In 1793, the regular troops were replaced by a caretaker garrison.

During the War of 1812, the fort was occupied by soldiers from the 99th and 104th Regiments along with members of the Royal Artillery. The fort was abandoned in 1835 on the recommendation of a commission established in the 1820s. Some of the buildings were dismantled while others were rented. By the beginning of the twentieth century, a few ruins in the middle of a field were all t h a t remained of a once imposing structure.