I'm not sure where, but today I came across a web page for the Chicago Cardinals football team. That started me on a quick little research track. It turns out that both of the original NFL teams still active have Chicago roots.
First, the Chicago Cardinals, who started playing in 1898 in Morgan Park, Chicago. They were called the Racine Normals at one point, but it was because they played on Racine, not in Racine. They eventually played at Comiskey Park on the South Side of the city, making them a football analog to the Bears, who played at Wrigley Field. Curley Lambeau coached the team in the early 1950s, before he went on to a career with the Green Bay Packers (as in Lambeau Field). The Cardinals have made the playoffs six times since 1932. They won the NFL title in 1947 and lost it in 1948. In 1944 the Cardinals temporarily merged with the Pittsburgh Steelers for the season to be the Card-Pitts (or Carpets). Finally, the Cardinals are called the Cardinals because they purchased faded used uniforms from the University of Chicago Maroons. The uniforms were "cardinal red" after fading from maroon.
Meanwhile, the Decatur Staleys moved to the Chi in 1921. They started playing at Wrigley Field in 1921 and moved to Soldier Field in 1970. The Bears have over 1000 games played in the NFL, and over 660 wins. George Halas modeled the Bears uniforms on the uniforms of his alma mater (and mine) Illinois. The Bears have won eight NFL championships and one Super Bowl championship, and been in the playoffs 22 times (now 23) since 1921. They are the opposite of the Cardinals.
Into the 1940s the NFL league offices were in Chicago.
Besides the Bears and Cardinals, Chicago has had several professional non-arena football teams from other leagues. The All-American Football Conference brought the Chicago Rockets from 1947 to 1948, and the Chicago Hornets for 1949. The 1926 incarnation of the American Football League brought the Chicago Bulls. The versions of the American Football League active in the 1930s, 1940s, and the 1950-60s respectively each skipped the Chi when doling out teams. The Continental Football League created the Chicago Owls for their 1968-69 seasons. The World Football League graced us with the Chicago Fire in 1974 and the Chicago Wind in 1975. In 1983 and 1984 the United States Football League entrant from Chicago was known as the Chicago Blitz. In 2001 the Chicago Enforcers played in the XFL.