[4] In 2020, a special Blue-Ribbon Panel selected an additional 15 new members, known as the "Centennial Slate", to be inducted into the Hall of Fame to celebrate the 100th anniversary of the National Football League (NFL).
[11] In addition to Shaw, there are 37 other inductees who spent all or part of their careers in the American Football League that merged with the NFL.
[12] Three players, Red Grange, Ray Flaherty, Mike Michalske, played a portion of their career in the first American Football League from 1926.
Ken Strong is the lone Hall of Fame inductee who played during the second iteration of the American Football League from 1936.
Six players or coaches who spent part of their careers in the original incarnation of the United States Football League (USFL) have been inducted.
[13] Two coaches (Marv Levy,[14] Bud Grant[15]), one administrator (Jim Finks), and five players (Warren Moon,[16] Fred Biletnikoff, John Henry Johnson, Don Maynard, Arnie Weinmeister) who spent part of their careers in the Canadian Football League (CFL) have been inducted.
Of these inductees, three have been or are scheduled to be inducted into the Canadian Football Hall of Fame: Marv Levy, Warren Moon and Bud Grant.
Four players, Larry Csonka, Leroy Kelly, Don Maynard, and Paul Warfield, played a portion of their career in the short-lived World Football League.
Bill Polian founded the Alliance of American Football, but he was inducted into the hall in 2015 and the league started in 2019.