Tongass Island, historically also spelled Tongas Island, is an island in the southern Alaska Panhandle, near the marine boundary with Canada at 54-40 N. it was the site of Fort Tongass, which was first established shortly after the Alaska Purchase as a customs port for travellers bound from British Columbian waters to the Stikine River, which was one of the main routes of access to the Cassiar Gold Rush of the 1870s. it lies west of Port Tongass in Nakat Bay, adjacent to the Dixon Entrance and is 0.8 miles in length.