Horseshoe Island is an island

Island

An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...

 6.5 nautical miles (12 km) long and 3 nautical miles (6 km) wide occupying most of the entrance to Square Bay

Square Bay

Square Bay is a bay, roughly square in outline and 10 nautical miles wide, indenting the west coast of Graham Land between Nicholl Head and Camp Point. Most of the entrance to the bay is occupied by Horseshoe Island, which limits access to a narrow southern strait opening onto Marguerite Bay and...

, along the west coast of Graham Land

Graham Land

Graham Land is that portion of the Antarctic Peninsula which lies north of a line joining Cape Jeremy and Cape Agassiz. This description of Graham Land is consistent with the 1964 agreement between the British Antarctic Place-names Committee and the US Advisory Committee on Antarctic Names, in...

. Discovered and named by the British Graham Land Expedition

British Graham Land Expedition

A British expedition to Graham Land led by John Lachlan Cope took place between 1920 and 1922. The British Graham Land Expedition was a geophysical and exploration expedition to Graham Land in Antarctica between 1934 to 1937. Under the leadership of John Riddoch Rymill, the expedition spent two...

(BGLE) under Rymill who mapped this area by land and from the air in 1936-37. Its name is indicative of the crescentic alignment of the 600 to 900 m peaks which give a comparable shape to the island.