A history of NHL expansion from the Original Six until the addition of Seattle as the 32nd franchise:
1942: Boston Bruins, Chicago Black Hawks, Detroit Red Wings, Montreal Canadiens, New York Rangers and Toronto Maple Leafs make up Original Six.
1967: Great Expansion doubles league in size to 12 with addition of California Seals, Los Angeles Kings, Minnesota North Stars, Philadelphia Flyers, Pittsburgh Penguins and St. Louis Blues.
1970: Buffalo Sabres and Vancouver Canucks join to give league 14 teams.
1972: Atlanta Flames and New York Islanders join to give league 16 teams.
1974: Kansas City Scouts and Washington Capitals join to give league 18 teams.
1978: After Seals' move to Cleveland, merger of Cleveland Barons and Minnesota North Stars gives league 17 teams.
1979: League absorbs Edmonton Oilers, Hartford Whalers, Quebec Nordiques and Winnipeg Jets from Western Hockey Association to get to 21 teams.
1991: San Jose Sharks become league's 22nd team to begin new era of expansion.
1992: Ottawa Senators and Tampa Bay Lightning join to give league 24 teams.
1993: Mighty Ducks of Anaheim and Florida Panthers join to give league 26 teams.
1998: Nashville Predators join to give league 27 teams.
1999: Atlanta Thrashers join to give league 28 teams.
2000: Columbus Blue Jackets and Minnesota Wild join to give league 30 teams.
2017: Vegas Golden Knights join to give league 31 teams.
2018: Seattle approved as 32nd team to begin play in 2021.