In their inaugural season, the Flyers finished atop the West Division, recording 73 points in 74 games. The California Seals, a pre-season favourite to win the division, changed their name to the Oakland Seals a month into the season. The team disappointed both on the ice and at the gate, finishing last in the NHL with 14 wins. The Blues defeated the Flyers and North Stars to become the first expansion team to play for the Stanley Cup, where they were defeated in four consecutive games by the Canadiens. The Blues reached the finals again in both 1969 and 1970, but were similarly swept in both years, losing to the Canadiens and Boston Bruins, respectively.
On January 13, 1968, North Stars' rookie Bill Masterton became the first and, to date, only player to die as a result of injuries suffered during an NHL game. Early in a game against the Seals, Masterton was checked hard by two players, Ron Harris and Larry Cahan, causing him to flip over backwards and land on his head. He was rushed to hospital with massive head injuries, and died there two days later. The National Hockey League Writers Association presented the league with the Bill Masterton Memorial Trophy later in the season; the trophy is awarded annually to the player who best exemplifies the qualities of perseverance, sportsmanship and dedication to hockey. Following Masterton's death, players slowly began wearing helmets; starting in the 1979–80 season, the league mandated that all players entering the league wear them.
In Canada, there was widespread outrage over the denial of an expansion team to Vancouver in 1967. Three years later, the NHL added a third Canadian team when the Vancouver Canucks, formerly of the Western Hockey League, were admitted as an expansion team for the 1970–71 season, along with the Buffalo Sabres. The Canucks were placed in the East Division, despite being on the west coast, while the Chicago Black Hawks were shifted to the West in an attempt to equalize the divisions' strength. The league also gave the Sabres and Canucks the first two picks in the 1970 NHL Amateur Draft, offering them a better opportunity to build their rosters than the 1967 expansion teams had.
Before the 1971–72 season, Gordie Howe and Jean Beliveau announced their retirements. Beliveau finished his 18-year career with 10 Stanley Cups, 2 Hart Trophies and 1,219 career points; his points total was the second-highest in NHL history. After playing 25 seasons in the NHL, Howe retired as the league's all-time leader in games played, goals, assists and points. Howe was a six-time league scoring champion, and also won six Hart Trophies. Both players had the customary three-year waiting period waived for entry into the Hockey Hall of Fame in acknowledgment of their achievements.
On February 7, 1976, Maple Leafs star Darryl Sittler set an NHL record, scoring 10 points in one game in an 11–4 victory over the Bruins. His six-goal, four-assist effort broke Maurice Richard's record of eight points in a game. The game came shortly after the Bruins lured Gerry Cheevers back from the WHA, though Cheevers was given an extra night to rest, and rookie Dave Reece was the victim of all 11 Toronto goals. It was his 14th, and final, NHL game.