Minden, a small city, produced other successful athletes too, including David Allen Lee (born 1943), the punter for the Baltimore Colts from 1966-1978, and Fred Haynes (1946-2006), the holder of many football records as the quarterback at Louisiana State University in Baton Rouge during the late 1960s.
Hennigan attended LSU on a track scholarship but wanted to play football. He therefore transferred to Northwestern State University (then Northwestern State College) in Natchitoches, where he became the star of the team. In 1960, he joined the American Football League's Houston Oilers in the team's first year of operation. Prior to joining the Oilers, he had taught high school biology at a salary of some $2,700 per year. He kept his teacher pay stub in his helmet to remind him that he must succeed in pro athletes.
Hennigan scored the first touchdown in Oilers history. After a promising rookie season, in 1961 he started all 14 games and established himself as a superstar in the AFL by gaining 1,746 yards receiving, a pro-football record that stood for 34 years. One of quarterback George Blanda’s main targets, Hennigan was the first professional football player to catch more than a hundred passes in a single season (101 in 1964) and to twice gain over 1,500 yards receiving (1961 and 1964). He holds the all-time records for most games in a season with over 200 yards receiving with three, and most games in a season with over 100 yards receiving with 11. Hennigan had the All-time AFL single game record of 272 yards receiving, against the Boston Patriots on October 16, 1961.
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.
On April 6, 2002, Hennigan, a Democrat, ran in a special election for Place 8 on the Caddo Parish Commission, his parish's governing body. He was defeated by Republican Michael Long. Long obtained 2,139 votes (74.9 percent) to Hennigan's 716 (25.1 percent).
Hennigan holds a doctorate in education from the University of Houston. He operates an educational tutoring service in Shreveport and works with prisoners seeking the General Equivalency Diploma (GED). Hennigan has seven children.