Allen is best remembered as the architect of the "Broad Street Bullies" Flyers teams that won the Stanley Cup in 1974 and 1975. His drafts brought in franchise stalwarts like fellow Hall of Fame member Bill Barber, Rick MacLeish, Bob Kelly and Bill Clement, and earned the nickname of "Keith the Thief" for trades that brought in goaltender Bernie Parent, defenseman Barry Ashbee and forwards Reggie Leach, Terry Crisp and Andre Dupont.
"Keith Allen always found a way to bring exceptional talent to Broad Street and weave it into the fabric of a team that would succeed and endure at the highest level, because in Philadelphia, for his Flyers and their fans, no other level was acceptable," NHL Commissioner Gary Bettman said in a statement.
"The National Hockey League sends heartfelt condolences to Keith's family, to his friends and to the Flyers organization, which has lost one of its patriarchs."
Allen joined the Flyers as the team's initial coach for the 1967-68 season after 13 seasons as a coach in the Western Hockey League. The Flyers went 31-32-11 in their first season to win the West Division, which was stocked with the League's six expansion teams.
After two seasons as coach Allen moved into the front office for the 1969-70 season, and replaced Bud Poile as general manager on Dec. 22, 1969. He held that title for 14 seasons. Along the way the Flyers made the playoffs 12 times, won six division titles and advanced to the Stanley Cup Final four times, including three straight years (1974-76). He retired after the 1982-83 season; the Flyers went 563-322-194 (.612 winning percentage) during his tenure.
He was inducted into the Hockey Hall of Fame as a Builder in 1992.
"Keith was the first coach in the history of the Philadelphia Flyers and a man for whom I have tremendous respect," Flyers chairman Ed Snider said in a statement released by the team. "In my mind he was and always will be one of the greatest general managers in the history of hockey. He was known as 'Keith the Thief,' [and] I never knew of a bad deal he made. This team would never have reached the level of success we have had over the past 48 years if it were not for Keith.
"Over the years he became one of my closest confidants and one of my best friends. I will never forget all of the many memories we shared together."
Allen also was at the helm of the 1979-80 Flyers team which went to the Stanley Cup Final and along the way set a League record with a 35-game unbeaten streak. He also set the foundation for the Flyers teams that would go to the Stanley Cup Final in 1985 and 1987. He drafted core members of that group like forwards Brian Propp and Rick Tocchet and goaltenders Pelle Lindbergh and Ron Hextall. He also signed forwards Tim Kerr, Ilkka Sinisalo and Dave Poulin as free agents.
"I think Keith never got nearly the credit for what he did that he should have," Bob Clarke, the captain of the Flyers' championship teams, told NHL.com.
Allen, born Aug. 21, 1923 in Saskatoon, was a defenseman who spent most of his 15 professional seasons in the minor leagues. He was a part of two Stanley Cup champions with the Detroit Red Wings, playing 10 regular-season and five playoff games with the Red Wings in 1953-54 and 18 regular-season games in 1954-55.
In 1955-56 he began his coaching career as the player/coach of the Brandon Regals of the Western Hockey League. He went into coaching full time following the 1956-57 season.