The narwhal, a marine mammal which inhabits Arctic seas and is related to the whale and the porpoise, has a single tusk which often grows to nine feet in length suggesting the horn of a unicorn. Indeed, the narwhal is frequently called the sea unicorn.
The contract for the construction of Unicorn (SS-429), a Tench-class submarine authorized on 9 July 1942 and scheduled to be built at Philadelphia, Pa., by the Cramp Shipbuilding Co., was cancelled on 29 July 1944.
The contract for the construction of Unicorn (SS-436), a Tench-class submarine laid down on 25 April 1945, at Groton, Conn., by the Electric Boat Co., was terminated on 7 January 1946. However, it was reinstated on 26 February 1946 for "completion of specific items." The submarine was launched on 1 August 1946; sponsored by Mrs. William A. Rowan; and accepted by the Navy on 3 September.
Towed to the Portsmouth (N.H.) Naval Shipyard on 15 September, the boat was moved to New London two months later and assigned to the Atlantic Reserve Fleet. She remained out of commission, in reserve, until 29 July 1958, when her name was struck from the Navy list.