It is located about 4.5 kilometres (2+3⁄4 miles) upstream from Horseshoe Falls, and has an area of roughly 1.2 km2 (7⁄16 sq mi).

It was designated a national historic site in 1921 in recognition of its role in shipbuilding and the location of the short-lived Republic of Canada.

The site is closed to the public, has no visitor facilities, and has not allowed camping since the expiration of a lease with the Niagara Parks Commission.

Archaeological excavations have revealed a native peoples burial site, along with their arrowheads and scrapers on the shores of the island.

[4][better source needed] During the French colonization of New France, Navy Island was known as Île de la Marina.

Farms and orchards were located on the northeast, south, central, northwest, and southwest ends of the island.

[8][better source needed] Navy Island was proposed to be the new World Peace Capital and headquarters of the United Nations by an international committee in 1945 and 1946.

An artist's rendering of the World Peace Capital showed the property with bridges spanning both countries (at Grand Island in the US and the Canadian mainland on the other side).

It was proposed that Navy Island would be ceded to the United Nations as long as the headquarters remained, and to revert to the Canadian government should the U.N. move.