The Chicago Cardinals.
The Cards-Bears rivalry actually began in 1920 when the Bears were known as the Staleys. It went on for nearly 40 years, with the two squads regularly playing each other twice per year until the early 1950s.
The rivalry was similar in many respects to the Cubs-White Sox rivalry that has developed in recent years due to interleague play (in fact, both the Bears and Cardinals regularly shared Wrigley Field and Comiskey Park as their home fields). The Cardinals were referred to as the south siders, while the Bears were the north siders. Fan allegiances to each team ran deep.
However, the inner city rivalry came to an abrupt end when the Cardinals moved to St. Louis prior to the start of the 1960 season. Little did anyone know that the November 29, 1959 contest between the Bears and Cards would be the last between two Chicago-based NFL squads.
It was the 70th meeting of the two teams, played in front of over 48,000 fans at Soldier Field. Tickets were $2.50 for reserved seats and $1.75 each for bleachers. Although the Bears held a commanding 44-19 record in the series (six games ended in a tie), the Cardinals did have a history of upsetting the Bears over the years in key games when the Bears were driving for a division title.
Going into this particular matchup, the Bears found themselves in the thick of the NFL Western Division race, just a game behind co-leaders San Francisco and the Baltimore Colts. The Cardinals, meanwhile, were mired in last place in the Eastern Division with a 2-7 mark.
The Bears' lineup featured Johnny Morris, Willie Galimore, Rick Casares, Jim Dooley and Abe Gibron (the latter two would go on to become Bears head coaches). Meanwhile, the Cardinals featured power and speed in their backfield with fullback John Crow and halfback Bobby Conrad.
Emotion always plays a big part when two rivals butt heads, and this meeting was no exception. After one particular play, Cardinal defensive end Leo Sugar took exception to a hit by Bear defender Erich Barnes on a Cardinal teammate and came off the bench to confront Barnes.
But this time around, the Cardinals wouldn't be a thorn in the Bears' side as the north siders dominated their rivals 31-7. The Bears took advantage of six Cardinal fumbles, while quarterback Ed Brown hooked up with Willard Dewveall (a Canadian Football League castoff) for two touchdowns.
The Cardinals called St. Louis home for the next 27 years, then moved to Phoenix in 1987 and became the Arizona Cardinals.