10 Oct 1979
After the World Hockey Association folded in 1979, the Edmonton Oilers and three other teams joined the NHL. Gretzky's success in the WHA carried over into the NHL, despite some critics suggesting he would flounder in what was considered the bigger, tougher, and more talented league. The Oilers, like the other surviving WHA teams, were allowed to protect two goaltenders and two skaters from being reclaimed by the established NHL teams, of which one skater was Gretzky.
Source/Attribution
Wikipedia
Added Tue, Jan 5 2010 at 2:21AM UTC by