At the outbreak of the
Civil War, Sampson enlisted in the
Union Army as a
captain in the
5th Iowa Volunteer Infantry Regiment in 1861 and was later promoted to
lieutenant colonel of the same regiment, serving as so until he was mustered out of service in 1864. After the war, he resumed practicing law in Sigourney. He was a member of the
Iowa Senate in 1866 and was judge of the sixth district of Iowa from 1867 to 1875. In 1874, Sampson was elected a Republican to represent Iowa's 6th congressional district in the
United States House of Representatives. Near the end of his service in the
44th United States Congress, he was re-elected in 1876 to a second term, and served in the
45th United States Congress. When running for a third term in 1878, he was defeated in the general election by
Greenback Party candidate (and future presidential candidate)
James B. Weaver. Sampson served in Congress from March 4, 1875 to March 3, 1879. ==Death==