Beginning his boxing career in 1950 while serving with the U.S. Navy, Greenhill won all 17 of his military bouts. Upon his return home, he joined the Durham Boxing Team and became an integral part of one of the better amateur teams in the state. He won 45 matches and lost only to the great Crowe Peele with Durham. After turning professional, Greenhill won another 20 bouts without losing. His overall boxing record stands at 82 wins, a single loss, and a draw.
Greenhill owned and operated Greenhill Electric Company for 39 years, and he remains active in the electrical business. He and his former wife are the parents of two sons and they have two grandchildren. He has been given the Outstanding Community Service Award by the State of North Carolina. Greenhill is a pilot, and he enjoys golf, bowling, and restoring old cars.