December 12, 1937 and December 13, 1970
On December 12, 1937, Chicago hosted Washington in the NFL Championship Game at Wrigley Field. The Bears hosted five championship contests at Wrigley (also 1933, 1941, 1943 and 1963.) This was Chicago's only loss among the five.
1937 marked Washington's first year in the NFL, having moved from Boston. Rookie and future Hall of Famer Sammy Baugh threw two fourth quarter touchdowns in 28-21 triumph.
Flash forward to December 13, 1970:
The Bears play their final game at Wrigley, a 35-17 win over Green Bay. The NFL and AFL merged before the 1970 season. The agreement included a new rule: NFL teams were to use stadiums wi
th a capacity of at least 50,000. Wrigley's capacity for football was around 45,000, including temporary seating.
Wrigley was indeed "The Friendly Confines" as the Bears posted 219 home wins, 89 losses and 22 ties from 1921 to 1970, plus two "road" wins against the Chicago Tigers.