The Original Six teams constituted the NHL for 25 seasons before the League's 1967 expansion. The two Canadian teams, the Canadiens and the Maple Leafs joined the NHL in 1917 and the other four teams joined between 1924-26.
The Great Depression and World War II lead to the dormancy of other established American and Canadian teams such as the Penguins. The period of exapansion came about in the late 1960s as owners got behind the idea and witnessed the growth of other sports leagues.
The Original Six arenas are as follows: Boston Garden, Chicago Stadium, Detroit Olympia, Madison Square Garden, Maple Leaf Gardens, and Montreal Forum.