Since being founded in 1917, the National Hockey League (NHL), which in its first two seasons started out as a three-team league and eventually grew to thirty-one in its current state, has expanded and contracted numerous times throughout its history. The following is a complete history of organizational changes in the NHL.
The next season, the NHL added two new teams, the Pittsburgh Pirates and the New York Americans. The Americans were stocked by purchasing the contracts of the Hamilton Tigers players, and the Tigers franchise was subsequently revoked by the league.
Midway through the 1926–27 season, the Toronto St. Patricks were sold and renamed the Toronto Maple Leafs. However, the NHL ruled that the team had to still officially use the St. Patricks name until the end of that season.
The Montreal Maroons withdrew from the league for the 1938–39 season, further reducing the number of teams in the NHL to seven, shrinking to the size the league was in 1925–26. Play continued for four seasons with seven teams, with one single league table instead of any conference or divisions.
The Oakland Seals were renamed the Bay Area Seals for two games before changing their name again to the California Golden Seals for their fourth season in 1970–71. The same season the NHL added two new teams, the Buffalo Sabres and the Vancouver Canucks, paying an expansion fee of $6 million each ($38.7 million today). The Sabres and the Canucks were placed in the East (partially as an effort to provide greater balance between the divisions, and also so they would have rivalries with the other two Canadian teams), while the Chicago Black Hawks moved to the West
Two more teams joined for the 1972–73 NHL season, the New York Islanders and the Atlanta Flames. With the competing World Hockey Association (WHA) starting that same season, the NHL was not able to raise its expansion fee from the price of two years earlier, $6 million ($35.9 million today), with the Islanders paying an additional $5 million ($29.9 million today) to the New York Rangers for infringing on their territory. The Islanders were placed in the East and the Flames were placed in the West.
Two more teams joined for the 1974–75 NHL season, the Washington Capitals and the Kansas City Scouts, but the ongoing competition from the WHA meant that the overall revenue stream of the NHL had not improved, so the league kept the expansion fee for new owners at the $6 million ($30.5 million today) of two years and four years earlier. The earnings situation for the new franchises was so poor that (at least) the Capitals were able to negotiate a reduction to a total fee of $2.85 million ($14.5 million today).
Following seven seasons of revenue draining competition, the NHL–WHA merger was completed for the start of the 1979–80 NHL season. Four teams came over from the WHA, paying an expansion fee of $7.5 million each ($25.9 million today). These new NHL teams were the Edmonton Oilers, the Hartford Whalers, the Quebec Nordiques, and the (original) Winnipeg Jets. This also doubled the number of Canadian teams in the league. Standing at 21 teams for twelve seasons, this was one of the longer stable periods of NHL history, though surpassed by the twenty-five seasons of the Original Six period, when no additions, moves nor name changes occurred.
The Nordiques were placed in the Adams Division, the Whalers in the Norris, and the Oilers and the Jets were both placed in the Smythe. The Washington Capitals moved from the Norris to the Patrick Division.
The 1991–92 season saw the dawn of rapid expansion and relocation in the NHL, which lasted for the next ten years, starting with the addition of the San Jose Sharks, paying an expansion fee of $45 million ($82.8 million today). The Sharks were placed in the Smythe Division with the other West Coast teams.
Two new teams joined the league the following season, the Ottawa Senators and the Tampa Bay Lightning, paying an expansion fee of $45 million each ($80.3 million today). The Senators were placed in the Adams Division, and the Lightning in the Norris, so all four divisions would have six teams each.
The following season, another team started play, the Atlanta Thrashers, paying the same expansion fee of $80 million ($120.3 million today) as the Predators paid a year earlier. The Thrashers were placed in the Southeast Division.
For its 2000–01 season, the NHL added the Columbus Blue Jackets and the Minnesota Wild, each paying the same expansion fee of $80 million ($116.4 million today) as Nashville and Atlanta paid in the previous two years. The Blue Jackets were placed in the Central Division, and the Wild in the Northwest, so all six divisions would have five teams each.
For the next 17 seasons, the NHL maintained 30 teams, the second longest period (after the Original Six period) of membership stability in its history.
On December 5, 2011, the NHL Board of Governors originally approved a conference realignment plan to move from a six-division setup to a four-conference structure. However on January 6, 2012, the National Hockey League Players' Association (NHLPA) rejected that proposed realignment. A new joint NHL-NHLPA plan was proposed in February 2013 as a modification of the previous plan with both the Columbus Blue Jackets and Detroit Red Wings moving to the East and the Winnipeg Jets moving to the West. The NHLPA officially gave its consent to the NHL's proposed realignment plan on March 7, and then the NHL's Board of Governors approved the realignment on March 14, to be implemented prior to the 2013–14 season. The league then announced the names of the divisions on July 19: the two eight-team divisions in the Eastern Conference would be the Atlantic Division and the Metropolitan Division, and the two seven-team divisions in the Western Conference would be the Central Division and the Pacific Division.
On June 22, 2016, the Board of Governors voted 30-0 to add an expansion franchise in Las Vegas for the 2017–18 season, charging an expansion fee of $500 million ($522 million today). The new team, the Vegas Golden Knights, were put into the Pacific Division.
On December 4, 2018, Seattle was announced as the location of the future thirty-second franchise to begin play in the 2021–22 season, with an expansion fee of $650 million. The new Seattle NHL team will be placed in the Pacific Division, while the Arizona Coyotes will be moved to the Central Division.
Despite statements from the NHL in recent years that no further expansion or even relocation was planned for the foreseeable future (a statement partially contradicted by the relocation of the Thrashers to Winnipeg), there have been rumors and talks of potential new sites for existing or new teams in various locations in the United States and Canada. Since Winnipeg received the Jets in 2011, potential markets for relocation that have seen action in recent years include Quebec City, Hartford, Houston, Saskatoon, Kansas City, and Southern Ontario (which would be Hamilton, Toronto or Markham, although the league has actively blocked all of the Southern Ontario efforts to date, citing territorial concerns with the Buffalo Sabres and Toronto Maple Leafs).