USS Semmes (DD-189/AG-24) was a in the United States Navy during World War II. She was the first Navy ship named for Commander (USN), Rear Admiral (CSN), Brigadier General (CSA) Raphael Semmes (1809–1877). Service history Semmes was laid down on 10 June 1918 by the Newport News Shipbuilding & Dry Dock Company, Newport News, Virginia; launched on 21 December 1918; sponsored by Mrs. John H. Watkins, granddaughter of Raphael Semmes; and commissioned on 21 February 1920. Semmes was used as a testbed for an experimental twin 4 inch gun mount, giving it an armament of five 4"/50 caliber guns rather than the normal armament for Clemson-class destroyers of four such guns. This armament was retained until at least 1931. A few months later, she was the first to navigate using only the Ambrose Channel pilot cable. Following shakedown, Semmes participated in exercises along the northeast coast until January 1921 when she sailed south for winter fleet maneuvers in the Caribbean. From there, she transited the Panama Canal to cruise off the west coast of South America and returned to the Caribbean in late February to conduct further exercises out of Guantanamo Bay. In late April, she resumed operations out of Norfolk, Virginia. The destroyer was ordered inactivated in 1922; and, on 12 April, entered the Philadelphia Navy Yard where she was decommissioned on 17 July 1922. Reactivated 10 years later, she was transferred to the United States Coast Guard to serve in the Rum Patrol. She was commissioned in that service on 25 April 1932. As a Coast Guard destroyer, she was reconditioned at Boston, Massachusetts and based at New London, Connecticut whence she operated from 25 September until detached for two months duty with the Navy on 7 September 1933. On 10 November, she returned to New London and resumed operations for the Treasury Department. On 20 April 1934, the destroyer was returned to the Navy and was recommissioned as an experimental ship in accordance with the London Treaty limiting naval armament. Although not officially redesignated as an auxiliary ship, AG-24, until 1 July 1935, Semmes was assigned to Experimental Division 1 and, with assigned submarines, tested and evaluated underwater sound equipment into the 1940s. In May 1939, Semmes took part in the recovery efforts for the submarine . Semmes was fitted with a prototype SG centimetric surface search radar in 1941. After the entry of the United States