Visitors to Fort Ontario State Historic Site today will see the star-shaped fort dating to the early 1840's with 1863 to 1872 improvements. The fort is currently open to the public and undergoing renovations to its two officer's quarters; one is unfurnished but there is a video showing the rooms as they appeared with furniture. There are two Guardhouses, a Powder Magazine, Storehouse, Enlisted Men's Barracks, and windswept ramparts featuring magnificent views of Lake Ontario and underground stone casemates and gallaries to tour.
The fourth and current Fort Ontario is built on the ruins of three earlier fortifications dating to the French and Indian War, Revolutionary War, and War of 1812. It was occupied by the U.S. Army through World War II. From 1944 to 1946 the fort served as the only refugee camp in the United States for mostly Jewish victims of the Nazi Holocaust under an Executive Order from President Franklin D. Roosevelt. A post cemetery containing the graves of 77 officers, soldiers, women, and children who servied at Fort Ontario in war and peace is situated on the grounds which are open year-round from dawn to dusk.
In 1946 Fort Ontario was transferred to the State of New York and housed World War II veterans and their families until 1953. It opened as a state historic site in 1953.