When Super Bowl XII was played in the New Orleans Superdome after the 1977 season, many people probably assumed it was the first National Football League title game played under cover. The distinction, surprisingly, goes to the first-ever NFL playoff game between Chicago and Portsmouth, Ohio, in 1931. Because the weather in Chicago remained frigid during the week preceding the Bears' 9-0 victory, the teams agreed to move the contest from Wrigley Field to Chicago Stadium.
Since the edge of the indoor field ran dangerously close to a wall, balls downed either out of bounds or close to it were put into play 10 yards from the sidelines. This means of spotting the ball proved so successful that hash marks (short yard markers set in from the sidelines) soon became standard.
The crmped quarters in Chicago Stadium, where the field measured 80 yards by 145 feet instead of the regulation 100 yards by 145 feet instead of the regulation 100 yards by 160 feet, may have contributed to the low score. A 0-0 deadlock was finally broken in the fourth quarter when Bronko Nagurski faked a goal-line plunge, then stepped back to flip a touchdown pass to Red Grange.
For Chicago to end its season playing on an expanse of concrete covered by dirt and sod seemed appropriate. The Bears, after all, had produced one of the most an .875 winning percentage with just 7 victories in 14 games. They managed six ties along the way, three scoreless ones to start the season, followed by a 2-0 loss to Green Bay, Chicago's lone defeat.