Samuel Powhatan Carter was born on August 6, 1819 at Elizabethton, Tennessee, United States; grandson of Landon Carter, and greatgrandson of John Carter, the oldest of the three children of Alfred Moore Carter (1784 - 1850) and his second wife, Evalina B. Parry.
Samuel was educated at Washington College in that state, a Presbyterian institution, and at Princeton, which he entered as a sophomore in 1837. He graduated from the Naval Academy at Annapolis in 1846.
On February 14, 1840, Carter was appointed midshipman in the navy, making his first cruise, 1840-43, on the sloop Dale, of the Pacific squadron. After serving on the steamer Michigan, stationed on the Great Lakes, and the frigate Potomac of the home squadron, he late in 1845 was ordered to the Naval Academy at Annapolis where he graduated with the class of 1846. On July 11 of that year he was promoted passed midshipman. His first duty in this rank was on board the ship of the line Ohio, from which vessel he witnessed the fall of Vera Cruz. After periods of service at the Naval Observatory and on board the frigate St. Lawrence of the Mediterranean squadron, he was ordered in 1850 to the Naval Academy as assistant professor of mathematics, where he remained until 1853. He was promoted master in 1854, and lieutenant in 1855. While attached to the steam frigate San Jacinto of the East India squadron, he participated in the attack on the Barrier Forts, Canton River, China, in 1856. From 1857 to 1860 he was assistant to the executive officer of the Naval Academy. The outbreak of the Civil War found him serving on board the steam sloop Seminole of the Brazil squadron. A letter written by Carter while on the Brazil station declaring his purpose to adhere to the Union in the event of war was widely published in his home state and led Andrew Johnson and other influential residents of east Tennessee to request his services in prosecuting the war in that quarter. Early in July 1861 he was detailed from the navy to "special duty at the War Department" and was ordered to proceed to east Tennessee for the purpose of organizing and drilling Unionist volunteers. In less than a month he had organized one full regiment and part of another, the first Unionist troops from Tennessee. A month later he was placed in command of a Tennessee brigade and in May 1862 he was made a brigadier-general of the volunteer army. Until the close of 1862 he commanded brigades; and from that time until mustered out of service, divisions. In 1862 he commanded the first important cavalry raid made by the Unionists, in which he defeated the Confederates at Holston, Carter's Station, and Jonesville, and destroyed much valuable property. This raid brought relief to Rosecrans then hard pressed at Murfreesboro and infused new life into the Unionist cavalry. Carter received the thanks of Gen. Halleck and was recommended for promotion to the rank of major-general. At the battle of Kinston, N. C. , in March 1865, he commanded the left wing of the Unionist army; and later that year, the 23rd Army Corps and the District of Goldsboro. On Mar. 13, 1865, he received the brevet of major-general of volunteers and on January 19, 1866, was honorably mustered out of service. While serving in the army Carter in 1863 was promoted lieutenant-commander in the navy, and in 1865 commander. On his return to the navy in 1866 he was made commander of the steamer Monocacy of the Asiatic squadron, in which capacity he served for three years. From 1870, in which year he received his captaincy, to 1873 he was commandant of midshipmen at Annapolis. He next saw active service for two years as commander of the steamship Alaska on the European station. His last important duty before his retirement in 1881 was as a member of the Light-House Board, 1877-80. In 1878 he was made a commodore and in 1882 he was advanced to the grade of rear-admiral on the retired list. He is buried in Oak Hill Cemetery, Washington, D. C.
He was the first and thus far only United States officer to have been commissioned both a general officer and a Naval flag officer. C. f. : Joseph D. Stewart, Major General, (United States Marine Corps) and Vice Admiral (United States Maritime Service), the USMS being a civilian agency. C. f. also: Rear Admiral and Brigadier General Raphael Semmes, Confederate States Navy and Army.
Carter was a member of the Light-House Board.
Carter was tall, handsome and dignified, graceful in carriage, and very affable. A fellow officer described him as a "soldierly Christian" of sincere piety and undoubted courage.
In 1877, Carter married Martha Custis Williams (1827–1899), a descendant of Martha Custis Washington.
