He was born in Thomaston, Maine to Ebenezer Thatcher and Lucy Flucker Knox, the daughter of Major General Henry Knox. Appointed to the U.S. Military Academy at West Point in 1822, Thatcher was absent on sick leave for most of the first year and resigned in April 1823. He then received an appointment as a midshipmanin the Navy on 4 March 1823. Thatcher spent most of the next four years on board the frigate in the Pacific. He became a passed midshipman on 4 March 1829, and in 1830-1831 served in the schooner and sloop of war in the West Indies. He was promoted to lieutenant on 28 February 1833 and served aboard the schooner in Chesapeake Bay. He then served on the frigate in the Mediterranean Squadron in 1834-35; had special duty in 1837; and returned to the Mediterranean in the frigate in 1840. He served aboard the receiving ship at Boston in 1843-46, then in the sloop-of-war, part of the Africa Squadron in 1847-50. After duty at Boston Navy Yard in 1851, he commanded the storeship in 1852. Promoted to commander on 14 September 1855, while serving as Executive Officer of the Naval Asylum at Philadelphia, Thatcher then commanded the small sloop of war in the Pacific in 1857-59. He was Executive Officer of the Boston Navy Yard from November 1859 to November 1861, and thus played a role in the vast expansion of the Navy that began with the outbreak of the Civil War in April 1861.
Thatcher remained in command in the Gulf of Mexico until May 1866, receiving promotion to rear admiral on 25 July 1866, and commanded the North Pacific Squadron in 1867-68. There he was presented with a medal and made a Knight of the Order of Kamehameha I by King Kamehameha V of the Hawaiian Islands, an honor that he was permitted to accept by virtue of a special Act of Congress. Though put on the retired list on 26 May 1868 when he reached the age of 62, Thatcher served as Port Admiral at Portsmouth, New Hampshire, in 1869-70. By right of his descent from his grandfather, Major General Henry Knox, Thatcher was a member of the Massachusetts Society of the Cincinnati. He became president of the Massachusetts Society in 1871. Thatcher and his family settled in Winchester, Massachusetts, where he spent the remaining nine years of his life. Rear Admiral Thatcher died at his home on 5 April 1880.
Namesakes
Two U.S. Navy destroyers have been named in honor of Rear Admiral Thatcher; , and .