In October 1945 Wesley Branch Rickey (1881–1965), general manager of the Brooklyn Dodgers, signed Jack Roosevelt Robinson (1919–1972) from the Negro League's Kansas City Monarchs to the Dodgers organization, thus breaking the color barrier that had existed in professional baseball since 1889. On April 15, 1947, Robinson took the field for the first time as a Brooklyn Dodger, earning the title "Rookie of the Year" in the National League at the end of the season with twelve homers, twenty-nine steals, and a .297 batting average. Shortly after Robinson's debut, Larry Doby was signed by the Cleveland Indians, who then brought over the Negro League's star pitcher, Satchel Paige, to join Doby the following year. With these developments, baseball's long-entrenched segregation began, slowly, to crumble; it took another twelve years for the Boston Red Sox—the last team to integrate—to hire Elijah "Pumpsie" Green, three years after Robinson retired from the game.
The selection of baseball cards illustrating some of the earliest and most illustrious players who moved from the Negro Leagues into the Majors is taken from the Jefferson R. Burdick Collection. The more than thirty thousand baseball cards collected by Burdick date from 1887 to 1959 and represent the most comprehensive collection outside of the Baseball Hall of Fame in Cooperstown, New York.