The Great Depression was an economic downturn that lasted from October, 1929, well into the late 1930's.
It had a great effect on hockey. The National Hockey League had 10 teams in 1926-27. By 1938-39 it was down to 7. The Pittsburgh Pirates, Philadelphia Quakers, Ottawa Senators, Montreal Maroons, and St. Louis Eagles were all victims of the depression. Also victims were possible expansion teams.