The South Shetland Islands are a group of Antarctic islands, lying about 120 kilometres (75 mi) north of the Antarctic Peninsula, with a total area of 3,687 square kilometres (1,424 sq mi). By the Antarctic Treaty of 1959, the Islands' sovereignty is neither recognized nor disputed by the signatories and they are free for use by any signatory for non-military purposes. The islands have been claimed by the United Kingdom since 1908 and have been part of the British Antarctic Territory since 1962. They are also claimed by the governments of Chile (since 1940, as part of the Antártica Chilena Province) and by Argentina (since 1943, as part of Argentine Antarctica, Tierra del Fuego Province). Several countries maintain research stations on the Islands. Most of them are situated on King George Island, benefiting from the airfield of the Chilean base Eduardo Frei. There are sixteen research stations to date in different parts of the islands, with Chilean stations being the greatest in number. Research is often a shared duty of nations, with Chilean-American Shirreff Base being an example of this.