The Baseball color line was the unwritten policy that excluded African American baseball players from Organized Ball in the United States before 1947. 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 Baseball Players decided to bar "any club including one or more colored persons." As baseball became a professional sport, 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 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 homogenous 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.
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.
Baseball's color barrier cracked on April 18, 1946 when Jackie Robinson, when Branch Rickey, with the support of the new baseball commissioner, Albert "Happy" Chandler, signed the African American player Jackie Robinson in 1946, intending him to play for the Brooklyn Dodgers in the National League. Robinson made his first appearance with the Montreal Royals in the International League, where he endured epithets and death threats. After a single season with Montreal, he joined the parent club and helped propel the Dodgers to a National League pennant. Along the way he also earned National League Rookie Of The Year honors.
Robinson's success opened the floodgates for a steady stream of black players into organized baseball. He was was shortly joined in Brooklyn by Negro League stars Roy Campanella, Joe Black and Don Newcombe, and Larry Doby became the American League's first black star with the Cleveland Indians. By 1952 there were 150 black players in organized baseball, and the "cream of the crop" had been lured from Negro League rosters to the integrated minors and majors.