The island was populated from 1887 to 1974 as a coal mining facility. The island's most notable features are the abandoned and undisturbed concrete apartment buildings and the surrounding sea wall. Mitsubishi bought the island in 1890 and began to extract coal from undersea mines. In 1959, the 6.3-hectare (16-acre) island's population reached its peak of 5,259. As petroleum replaced coal in Japan in the 1960s, coal mines began shutting down all over the country, and Hashima's mines were no exception. Mitsubishi officially announced the closing of the mine in 1974, and today it is empty and bare. Travel to Hashima was re-opened on 22 April 2009 after 35 years of closure. A full re-opening of the island would require an enormous amount of money to make the premises safe, due to the aging of the buildings.
It is part of the prison island swims.
Hashima Island (commonly called Gunkanjima, meaning Battleship Island) was formally approved as a UNESCO World Heritage site in July 2015, as part of Japan's "Sites of Japan’s Meiji Industrial Revolution: Iron and Steel, Shipbuilding and Coal Mining.
Gunkanjima (gunkan meaning battleship, jima being the rendaku form of shima, meaning island), the island's nickname, came from its resemblance to the Japanese battleship Tosa. During the World War II era, the island was allegedly referred to as the "Jail Island" or "Hell Island" among Korean forced laborers. Beginning in the 1930s and up until the end of the Second World War, Korean conscripted civilians and Chinese prisoners-of-war were forced to work under very harsh conditions and brutal treatment at the Mitsubishi facility as slave laborers under Japanese wartime mobilization policies.