CHICAGO - The NFL's first game played indoors happened completely by accident. In fact, the game itself wasn't even on the schedule until the end of the season.
The Chicago Bears and the Portsmouth Spartans both went undefeated in the 1932 season. In those days, the NFL declared the team with the best record to be champion, with head-to-head matchups deciding any tiebreakers. The problem was that Chicago and Portsmouth had played to a pair of ties in their two meetings, so no tiebreaker could be used. The league reluctantly decided to hold a postseason playoff game.
The game was scheduled for December 18 at Wrigley Field. Then, the snow started to fall. And it snowed and snowed and snowed. The blizzard was so bad that Wrigley Field was unplayable. Out of options, the NFL decided to play the game indoors at Chicago Stadium.
The setup made for some strange conditions. The 80-yard-long field was covered in dirt, rather than grass. Because the field was shorter than standard, the ball was moved back to the 20-yard line whenever a team crossed midfield. And the goalposts were moved to the back of the end zone rather than their normal spot on the goal line. Because the field budded right up against the walls, on-field hashmarks were used for the first time.
While the field was shorter than normal, it was also about 10 yards narrower, and so the defenses dominated. It took until the fourth quarter for somebody to score, and even that score was controversial. Chicago's Bronko Nagurski threw what appeared to be a touchdown pass to Red Grange to put Chicago ahead, but Portsmouth argued the call. At the time, a player couldn't throw a forward pass unless he was at least five yards behind the line of scrimmage, and Portsmouth argued that Nagurski was too close. Officials let the call stand, however, and Chicago had a 7-0 lead. The Bears later added a safety to make the final 9-0.
The unideal conditions notwithstanding, the game was popular with NFL fans. The forced led the NFL to go against its long-standing policy of no postseason games and establish a championship game to be played at the end of the season. Other rule changes, including allowed forward passes from anywhere behind the line of scrimmage, were inspired by this game and helped the NFL separate itself from college football. Indoor football didn't become a trend, though; the next NFL game to be played indoors was in 1968, when the Houston Oilers moved into the Astrodome.