It was first seen and mapped as an island in December 1893 by a Norwegian Sealing expedition under C.A.

Larsen, who named it after the Castor, a ship which combined sealing and exploring activities along the west coast of the Antarctic Peninsula under Captain Morten Pedersen in 1893–94.

[1] The feature was determined to be a nunatak in 1902 by the Swedish Antarctic Expedition under Otto Nordenskiöld.

[2] This article incorporates public domain material from "Castor Nunatak".

This Oscar II Coast location article is a stub.