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 separation's beginnings occurred in 1868, when the National Association of Base Ball Players decided to bar "any club including one or more colored persons." As baseball made the transition toward becoming a professional sport over the next decade, and the NABBP dissolved into competing organizations in 1871, professional players were no longer restricted by this rule, and for a short while – in 1878 and again in 1884 – African American players played in the big leagues. Over time, they were slowly excluded more and more. As prominent players such as Cap Anson, John McGraw, and Ty Cobb steadfastly refused to take the field with or against teams with African-Americans on the roster, it became informally accepted that African Americans were not to participate in Major League Baseball. The minor leagues were segregated by the end of tte 1898 season.
On May 28 1916, Jimmy Claxton temporarily broke the professional baseball color barrier when he played one game for the Oakland Oaks of the Pacific Coast League. Claxton was introduced to the team owner by a part-Indian friend as a fellow member of an Oklahoma tribe. Within a week, a friend of Claxton revealed that he had both African American and Native American ancestors, and was promptly fired. It would be nearly thirty more years before another black man played organized white baseball.
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.
During his term in office as the first baseball commissioner, Kenesaw Mountain Landis has been alleged to have been particularly determined to maintain the segregation. It is possible that he was guided by his background as a federal judge, and specifically by the then-existing constitutional doctrine of "separate but equal" institutions. He himself maintained for many years that black players could not be integrated into the major leagues without heavily compensating the owners of Negro League teams for what would likely result in the loss of their investments. In addition, integration at the major league level would likely have necessitated integrating the minor leagues, which were much more heavily distributed through the rural U.S. South and Midwest.
One disincentive to desegregation was that strong players who were white sometimes threatened to quit any team that took on a black player.
In 1943, baseball executive Bill Veeck attempted to buy the Philadelphia Phillies franchise; rumors began circulating that he intended to purchase the contracts of several Negro Leaguers in order to make the longtime also-rans more competitive in a period when war requirements had depleted most rosters. However, the franchise was instead sold to a different ownership group, and some historians have recently questioned the likelihood of Veeck's rumored intentions.
The color line was formally breached when Branch Rickey, with the support of the new baseball commissioner, Albert "Happy" Chandler, signed the African American player Jackie Robinson in October 1945, intending him to play for the Brooklyn Dodgers in the National League. After a year in the minor leagues with the Montreal Royals (International League), Robinson endured epithets and death threats and got off to a slow start in his first major league season in 1947, but his athleticism and skill earned him the Rookie of the Year award. Less well-known was Larry Doby, who signed with the Cleveland Indians that same year to become the American League's first African-American player. Both men were later elected to the Baseball Hall of Fame. Due to their success, teams slowly but surely integrated talented African-Americans on their roster.
Prior to the integration of the major leagues, the Brooklyn Dodgers spearheaded the integration of the minor leagues. Jackie Robinson and John Wright were assigned to Montreal, but also that season Don Newcombe and Roy Campanella became members of the Nashua Dodgers in the New England League. Nashua was the first minor-league team based in the United States to integrate its roster after 1898. Subsequently that season, the Pawtucket Slaters, the Boston Braves' New England League franchise, also integrated its roster, as did Brooklyn's franchise in Trois Riviers, Quebec. The rest of the minor leagues would slowly integrate as well, including those based in the Southern United States. The Carolina League, for example, integrated in 1951 when the Danville Leafs signed Percy Miller Jr. to their team.
The Boston Red Sox were the last major league team to integrate, due to the steadfast resistance provided by owner Tom Yawkey and manager Mike "Pinky" Higgins. However, they too eventually conformed to the integrationist trend, signing Pumpsie Green in 1959.