"Britain gained control of Fort Niagara in 1759, during the French & Indian War, after a nineteen-day siege. The British held the post throughout the American Revolution but were forced, by treaty, to yield it to the United States in 1796. " https://oldfortniagara.org/history/ Would seem to exceed the Evacuation of New York date quoted below: "On November 25, 1783, the British Army boarded their naval vessels and Evacuated New York City (then only coterminous with New York County), their wartime Headquarters and their last military position in the United States during the Revolutionary War." Rolland Miner Fogg of War, Book II - Assault on Carillon 1758 An Historical Novel of the F&I War www.minerbooks.info www.lulu.com/content/491665