1) the National Football League (NFL), which evolved from the first professional league, the American Professional Football Association; and
2) the American Football League, (AFL), a successful league from 1960 through 1969, with which the NFL eventually merged.
At its inception in 1920, the American Professional Football Association had several African-American players (a total of thirteen between 1920 and 1933). However, by 1932 the subsequent National Football League had only two black players, and by 1934 there were none. This disappearance of black players from the NFL effectively coincided with the entry of one of the leading owners of the league, George Preston Marshall. Marshall openly refused to have black athletes on his Boston Braves/Washington Redskins team, and reportedly pressured the rest of the league to follow suit. The NFL did not have another black player until after World War II.
In 1946, the Cleveland Browns of a rival pro football league, the All-America Football Conference, signed two black players: Marion Motley and Bill Willis. Slowly, black players began to be recruited by the NFL, with the L.A. Rams' signing of Woody Strode and Kenny Washington. Still, Marshall was quoted as saying "We'll start signing Negroes when the Harlem Globetrotters start signing whites." In spite of this open bias, Marshall was elected to the NFL's "pro football" hall of fame in 1963. As part of his "qualifications" for enshrinement, the hall says: "Marshall was totally involved in all aspects of his team’s operation and endured his share of criticism for not integrating his team until being forced to do so in 1962." The Redskins had no black players until they succumbed to the threat of civil-rights legal action by the Kennedy administration.
Even when the NFL did sign black players, poor treatment was evident. Reportedly, black players routinely received lower contracts than whites in the NFL, while in the American Football League there was no such distinction based on race (Miller Farr, in the foreword to The "Foolish Club" by Jim Acho, Gridiron Press, 1997).
Conversely, the American Football League actively recruited players from small colleges that had been largely ignored by the NFL, giving those schools' black players the opportunity to play professional football. As a result, for the years 1960 through 1962, AFL teams averaged 17% more blacks than NFL teams did. (Reference: Outside the Lines: African Americans and the Integration of the National Football League. By Charles K. Ross. New York: New York University Press, 1999, ISBN 0-8147-7495-4). By 1969, a comparison of the two league's championship team photos showed the AFL's Chiefs with 23 black players out of 51 players pictured, while the NFL Vikings had 11 blacks, of 42 players in the photo. The American Football League had the first black placekicker in professional football, Gene Mingo of the Denver Broncos; and the first black quarterback of the modern era, James Harris of the Buffalo Bills.