Born in Roanoke, Virginia, Hart attended Forest Park Academy. He received an Artium Baccalaureus degree from Virginia Military Institute in 1927 and a Bachelor of Laws from Harvard Law School in 1930. He was admitted to the District of Columbia bar in 1930. He was in private practice in Washington, D.C. at Lambert & Hart from 1930 to 1941. He was in the United States Army Reserve during World War II from 1941 to 1946. He became a captain in artillery, then served in the United States Army Air Force, rising to the rank of colonel in the United States Air Force when it became a separate service. He returned to private practice from 1946 to 1958.
