The Chicago Bears started playing as the Decatur Staleys as a charter member of the American Professional Football Association (APFA). George Halas became the team’s first organizer and coach of the team. He controlled the team until his death in 1983. Halas was the alumni the University of Illinois, where his college team wore orange-and-blue colors. The Bears adopted those colors as their own, in a darker shade of each. The Bears has always been the Halas’ legacy and is currently owned by Halas' grandson Michael McCaskey. On September 17, 1920, Halas along with the representatives of 11 other teams met in Canton, Ohio, and founded the American Professional Football Association, the precursor of the NFL.

The Bears won the new league’s first title in 1921, and a year later Halas and Sternaman baptized the team the Bears. Halas gave a very logical reason for naming the team Bears. He stated that since football players were generally bigger than baseball players and the city’s baseball team was known as Cubs, his football team should definitely be the bears. The Bears since their inception established themselves as one of the most successful and innovative team. The Bears were absorbed by the NFL in 1922. From 1921 to 1928, Halas and Sternaman led the team to eight straight winning records. The team won two NFL titles in the 1930s and four in the '40s. After winning the 1946 championship, they made the playoffs just twice in 17 years and failed to win another title until 1963. In 1963, Coach George Allen improved the team’s defensive skills. His line-up featured future Hall of Fame members’ defensive end Doug Atkins, linebacker Bill George, and tackle-guard Stan Jones. The offense was anchored by Mike Ditka. He completely revolutionized the tight end position and went on to become one of the league’s best pass receivers. The 1963 Bears defeated the New York Giants 14-10 for the NFL title. Halas retired as head coach in 1968. His retirement sent the team into a cellar for posting the worst record ever at 1-13.

Though the team inaugurated their new stadium Soldier Field in 1971, but continued to post losing seasons from 1970 through 1975. The Bears after recording several mediocre seasons made their first playoff appearance in 14 years in 1977. Ditka returned to the in 1982, but this time as a head coach and geared the Bears to six Central Division titles from 1984 to 1990 and one Super Bowl victory in 1985. Ditka’s offensive line-up featured running back Neal Anderson, wide receiver Willie Gault, and quarterback Jim McMahon. Ditka prior to his retirement in 1992 geared the Bears to three more Central Division titles. Former Dallas Cowboys defensive coordinator Dave Wannstedt replaced Ditka and reinvigorated the team in mid-1990s. Under his guidance, the Bears continued to struggle, making it necessary to fire Wannstedt following the 1998 season.

The Bears share one of the fiercest rivalries in professional sports with the Green Bay Packers. Once, the Bears were also responsible for starting the NFL's long-standing rule according to which a player could not be signed until he graduates his senior class. Consequentially the Bears’ impulsively signed U of I player Red Grange, who was immediately signed by the Bears following his final game as a collegian.