The color line, also known as the color barrier, in American baseball excluded players of black African descent from Major League Baseball and its affiliated Minor Leagues until 1947 (with a few notable exceptions in the 19th century before the line was firmly established). Racial segregation in professional baseball was sometimes called a gentlemen's agreement, meaning a tacit understanding, as there was no written policy at the highest level of organized baseball, the major leagues. A high minor league's vote in 1887 against allowing new contracts with black players within its league sent a powerful signal that eventually led to the disappearance of blacks from the sport's other minor leagues later that century, including the low minors.