Greenland was a large island on Earth located in the Northern Atlantic Ocean. The island was near to the coast of Canada and halfway between North America and Europe.
In 2254, when the Talosians downloaded a map of the Atlantic region from the library computer of the USS Enterprise, Greenland was one of the areas which was displayed. (TOS: "The Cage")
Greenland is under the political control of Denmark, but the USS
Enterprise map simply listed the region as "Greenland".