Congressman. Mann was born in Greenville on April 27, 1920, the son of Alfred Clio Mann and Nina Mae Griffin. His father was an attorney and mayor of Greenville. Mann attended the Greenville city schools and graduated with an A.B. degree from the Citadel in 1941. He entered the U.S. Army as a second lieutenant on July 24, 1941, and served forty-six months overseas during World War II. He rose to the rank of lieutenant colonel before his discharge on March 1, 1946. He married Virginia Thomason Brunson of Charleston on January 15, 1945. They have two children.
After World War II, Mann entered the University of South Carolina Law School, where he edited the South Carolina Law Review and was elected to Phi Beta Kappa. He graduated magna cum laude in 1947 and began to practice law with the firm of Mann, Arnold, and Mann in Greenville. He was elected to the state House of Representatives in 1948 and served two terms (1949–1952). In 1953 he was appointed solicitor of the Thirteenth Judicial Circuit. He was elected to two terms, serving from 1953 to 1963, when he returned to the practice of law. He served as president of the Greenville Chamber of Commerce (1965).
Mann was elected to the U.S. Congress in 1968 and served from 1969 to 1979. His most notable service was as a member of the Judiciary Committee during the impeachment of Richard Nixon. He crafted portions of the first and second Articles of Impeachment so as to make them acceptable to both Republicans and southern colleagues. On July 27, 1974, the committee voted (twenty-seven to eleven) in favor of impeachment.
In 1975, with the support of U.S. Senator Strom Thurmond, President Gerald Ford was prepared to nominate Mann to the U.S. Court of Military Appeals. Mann declined the appointment, however, citing the lack of opportunity for service offered by the position. Leaving Congress in January 1979, Mann resumed his law practice in Greenville.
Mann, James R. Papers. Modern Political Collections, South Caroliniana Library, University of South Carolina, Columbia.