Born in Saskatoon, Saskatchewan, Mr. Allen had a lengthy minor-league career as a defenseman in the American Hockey League and the Western Hockey League. He appeared in 28 games for the Detroit Red Wings over the 1953-54 and 1954-55 seasons, collecting four assists. He then coached for nine years in the WHL, guiding the Seattle Totems to a league championship in 1960.
Hired by Flyers chairman Ed Snider in 1967 when the National Hockey League expanded, Mr. Allen compiled a 51-67-33 record over the team's first two years of existence. But it was as their general manager that Mr. Allen had his greatest impact on the Flyers.
In the 1969 draft, Mr. Allen's first as GM, the Flyers selected Clarke - who would go on to become their all-time leading scorer and greatest player - in the second round and forwards Dave Schultz and Don Saleski in the fifth and sixth rounds, respectively. He hired the innovative Fred Shero as head coach in 1971, and Mr. Allen's first three picks in the 1972 draft were left wing Bill Barber and defensemen Tom Bladon and Jim Watson.
Finally, in his masterstroke, Mr. Allen traded goaltender Doug Favell and a first-round draft pick to the Toronto Maple Leafs in 1973 to reacquire goalie Bernie Parent. With Shero's hire and that succession of player-personnel decisions, Mr. Allen had assembled the nucleus of the "Broad Street Bullies," the nickname for the Flyers' rugged, physically intimidating teams of the 1970s.
"In my mind, he was and always will be one of the greatest general managers in the history of hockey," Snider said in a statement. "He was known as 'Keith the Thief.' 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."
Over Mr. Allen's final 10 seasons as Flyers general manager - he took an advisory position in their front office in May 1983 - the team won six division titles and their two Stanley Cups, reached the Finals two additional times, and during the 1979-80 season unfurled a 35-game unbeaten streak that remains an NHL record.
"He was everything," said Bill Clement, a forward on the Flyers' two Cup teams who analyzes the team for Comcast SportsNet. "He was strong. He was decisive. He cared about his players. He was a brilliant mind.
"More than anything, he was just a charismatic figure wherever he went. I talk about Keith in terms of reverence. He was everything a leader needed to be."
Mr. Allen received the Lester B. Patrick Trophy in 1988 to acknowledge his contributions to hockey within the United States, and four years later, he was inducted into the Hockey Hall of Fame.
"He more than anybody was responsible for us winning two Stanley Cups," Clarke said. "Keith was one of those men you very rarely come across who was fatherly and grandfatherly to all us players and our families and yet was tough enough and strong enough to do the things that were necessary so we had the right players to win a Stanley Cup.
"Every player who ever played here under his leadership liked Keith. He was one of the few men in hockey, maybe one of the only men, who everybody liked. He didn't have a person who disliked him in the world."
Mr. Allen is survived by his wife, Joyce; their sons, Brad and Blake; their daughter, Traci; and four grandchildren. Funeral arrangements were pending.