The baseball color line was the policy, unwritten for nearly its entire duration, which excluded African American baseball players from organized baseball in the United States before 1946. As a result, various Negro Leagues were formed, which featured those players not allowed to participate in the major or minor leagues. The Negro National League was founded in 1920 by Rube Foster. This created two parallel major leagues, and until 1947, professional baseball in the United States was played in separate homogeneous leagues.