 The NHL added another six teams by 1974 to bring the league to 18 teams . This continued expansion was partially brought about by the creation of the World Hockey Association ( WHA ) , which operated from 1972 until 1979 and sought to compete with the NHL for markets and players . Bobby Hull was the most famous player to defect to the rival league , signing a $ 2 @.@ 75 million contract with the Winnipeg Jets . When the WHA ceased operations in 1979 , the NHL absorbed four of the league 's teams — the Edmonton Oilers , Hartford Whalers , Quebec Nordiques and Winnipeg Jets . This brought the NHL to 21 teams ( the Cleveland Barons had ceased operations in 1978 ) , a figure that remained constant until the San Jose Sharks joined as an expansion franchise in 1991 . 
