His mother, Lura E. Hennigan (1916–1997), was a Pentecostal minister, piano teacher, and artist. She wrote a regular column entitled "The Abundant Life" for the Minden Press-Herald. Hennigan graduated in 1953 from Minden High School, where he excelled in football, basketball, and track as well as academics. Hennigan was selected by his peers as a Sporting News AFL All-League offensive end in 1961, 1962, and 1964. He was an American Football League Eastern Division All-Star five straight years (1961 - 1965), and retired after the 1966 season. He was selected to the All-Time All-AFL Second Team.