Why did Black baseball players increasingly join all-Black teams in the early 1900s?

In the early 1900s, Black baseball players increasingly joined all-Black teams primarily because they were excluded from the major and minor leagues by a tacit "gentlemen’s agreement" among the leaders of organized baseball.123

While no official rule explicitly banned Black players, the color line was gradually enforced through local customs and discriminatory practices, particularly as the 20th century dawned and racial segregation became more entrenched in both the North and the South. As opportunities in white professional leagues vanished, talented Black players formed their own high-quality teams in the Northeast and Midwest to continue their careers.12

These all-Black teams provided a professional outlet for players who were otherwise barred from the white leagues, allowing them to compete against one another for the "colored championship of the world" and play against white semipro and college teams. This development eventually led to the formation of organized associations such as the Negro National League and the Negro American League, which served as the primary professional home for African American athletes until the integration of Major League Baseball began in 1947.1243