For many decades, Black players could not play in Major League Baseball due to an unofficial “color line.” Instead, they formed their own leagues, generally known as “Negro Leagues.” The quality of baseball was quite good and many Negro League players would likely have been big stars in MLB had they been permitted to play.
Jackie Robinson, of course, broke that line in 1947 and Black players soon became some of the best players in MLB, including Willie Mays, Frank Robinson, Henry Aaron and others.
Until now, though, the Negro Leagues had been consigned to kind of a limbo in baseball history.