|Builder:||Fairchild Aircraft, East Farmingdale Long Island, New York|
|Laid down:||8 June 1954|
|Launched:||7 September 1955|
|In service:||7 October 1955|
|Out of service:||2 December 1957|
|In service:||December 1960|
|Out of service:||16 February 1973|
|Length:||49 ft 6 in (15.09 m)|
|Beam:||7 ft (2.1 m)|
|Draft:||6 ft 2 in (1.88 m)|
X-1 (or SS X-1) was the United States Navy's only midget submarine (but see the NR-1 Deep Submergence Craft), laid down on 8 June 1954, at Deer Park, Long Island, New York, by the Engine Division of Fairchild Engine and Airplane Corporation, launched on 7 September 1955, at Oyster Bay, Long Island, by Jakobson Shipyard; delivered to the Navy on 6 October at New London, Connecticut, and placed in service on 7 October 1955, with Lieutenant Kevin Hanlon in command.
X-1 served in a research capacity in rigorous and extensive tests to assist the Navy to evaluate its ability to defend harbors against very small submarines. Further tests conducted with the X-1 helped to determine the offensive capabilities and limitations of this type of submersible.
X-1 was originally powered by a hydrogen peroxide/diesel engine and battery system, but an explosion of her hydrogen peroxide supply on 20 May 1957 resulted in the craft's modification to accept a diesel-electric drive. On 2 December 1957, X-1 was taken out of service and deactivated at Philadelphia.
Towed to Annapolis, Maryland, in December 1960, X-1 was reactivated and attached to Submarine Squadron 6 and based at the Small Craft Facility of the Severn River Command for experimental duties in Chesapeake Bay. In tests conducted under the auspices of the Naval Research Laboratory, X-1 performed for scientists who observed her operations from a platform suspended beneath the Bay Bridge, to learn more about the properties and actions of sea water.
Remaining in an active, in-service, status through January 1973, X-1 was again taken out of service on 16 February 1973, and, on 26 April, was transferred to the Naval Ship Research and Development Center, Annapolis. On 9 July 1974, the submersible was slated for use as a historical exhibit; and she was subsequently placed on display on the grounds of the Naval Station complex, North Severn, near Annapolis. In 2001, X-1 was transferred to the Submarine Force Museum in Groton, Connecticut where it is on display in front of the main exhibit building.