I have already written a post on this topic. My central query was why segregation lasted as long as it did in major league sports. I have since learned more:
1. Black players were common in professional football in the late 19th century and through 1933, when segregation was introduced by team owners.
2. The pressure to segregate came from fan demand, and was enforced by game commissioners, working through a collusive league structure.
3. John McGraw, manager of the New York Giants (baseball), regularly tried to sneak African-Americans onto his team, claiming that they were “Cuban.” The baseball commissioner was both strong and racist, however, so he failed in these attempts.
4. Early football leagues were chaotic and had little power, including little power to enforce segregation in the early days of the sport.
5. Paul Brown, coach of the Cleveland Browns football team, decided to play black players in 1946.
6. The Los Angeles Rams quickly followed suit, in part because they wanted public funds for a stadium, and needed to avoid possible legal problems.
7. The Washington Redskins were the last football team to integrate, and only when they received “artfully applied pressure” from the Kennedy Administration.
8. Bill Walsh, the very successful coach of the San Francisco 49ers, hired a racially conscious sociologist to his staff, in recent times, to manage race relations on his team.
All points are from the recent and excellent Tackling Jim Crow: Racial Segregation in Professional Football, by Alan H. Levy.