NFL's 1st decade was the 1920s, when teams came and went
How Many NFL Teams Are There and Who Were the Original 8 Teams?
NFL's first game played in Dayton, Ohio
Arizona Cardinals Team History and Timeline - Sports Illustrated
The NFL's First Game Was Played in Dayton
The NFL: 100 Years of football - Los Angeles Times
The Super Bowl: History of America's Greatest Game
American football - College, Golden Age, Rules
National Football League - Wikipedia