The Cleveland Browns are a professional American football team based in Cleveland, Ohio. They play in the Northern division of the American Football Conference (AFC) in the National Football League (NFL). The Cleveland Browns began play in 1946 as a charter member of the All-America Football Conference and joined the NFL in 1950 after the AAFC folded. The team won all four AAFC titles and had one undefeated season (1948 - 15–0), as well as four NFL Championships.

1946–1949: The AAFC years

The Cleveland Browns were founded in 1946 as a charter member of the All-America Football Conference, under businessman Arthur B "Mickey" McBride. Not long after gaining the franchise, McBride named Ohio State Buckeyes coach Paul Brown as vice president, general manager and head coach. The franchise conducted a team naming contest in 1945. The most popular submission was "Browns" in recognition of Paul Brown, already an established and popular figure in Ohio sports. Brown at first objected to the name and the team selected from the contest entries the name "Panthers." However, after an area businessman informed the team that he owned the rights to the name Cleveland Panthers from an earlier failed football team, Brown rescinded his objection and agreed to the use of his name.

Brown parlayed his ties to the Buckeyes and the Navy (where he'd coached a base football team during World War II) into the most extensive recruitment network that had ever been seen at the time in pro football. He used it to assemble a team that, in terms of talent, would have been more than a match for any NFL team—including quarterback Otto Graham, kicker/offensive tackle Lou Groza, wide receiver Mac Speedie, fullback Marion Motley and nose guard Bill Willis. The Browns dominated the AAFC, winning all four of its championships including the 1948 season in which they became the first unbeaten and untied team in professional football history—24 years before the NFL's perfect team, the 1972 Miami Dolphins. Cleveland's undefeated streak (including 2 ties) reached 29 games, and included 18 straight wins and the 1947 and 1948 AAFC championship games. During the AAFC's four-year run, the Browns lost only four games. The Browns issued occasional challenges to NFL teams, only to be turned down almost out of hand each time.

Thanks in large part to McBride's promotional efforts, the Cleveland area showed terrific support for the Browns from the moment they were created. The team saw a record setting average attendance of 57,000 a game in its first season. The Browns unexpectedly had Cleveland to themselves; the NFL's Cleveland Rams, who had continually lost money while in Cleveland despite winning the 1945 NFL championship, moved to the booming area of Los Angeles after the 1945 season (the team is now located in St. Louis).