First NFL Championship Game

December 18, 1932:

The Chicago Bears defeat the Portsmouth Spartans 9-0 in the first ever NFL Championship Game. Because of a blizzard, the game is moved from Wrigley Field to the Chicago Stadium, the field measuring 80 yards (73 m) long.
In the 1932 season, the Chicago Bears and the Portsmouth Spartans tied with the best regular-season winning percentages (although the Green Bay Packers had four more wins). To determine the champion, the league voted to hold the first official playoff game in Chicago at Wrigley Field. Because of severe winter conditions before the game, and fear of low turnout, the game was held indoors at Chicago Stadium which forced some temporary rule changes. The game was played on a modified 80-yard dirt field, and Chicago won 9–0, winning the league championship. A number of new rule changes were instituted, many inspired by the 1932 indoor championship game: the goal posts were moved forward to the goal line, every play started from between the hash marks, and forward passes could originate from anywhere behind the line of scrimmage (instead of five yards behind). The playoff game proved so popular that the league reorganized into two divisions for the 1933 season, with the winners advancing to a scheduled championship game.

More on the game here.  More on Portsmouth's NFL history here.