Jackie Robinson of the Kansas City Monarchs signs a contract for the Brooklyn Dodgers, breaking the baseball color line.

Jack Roosevelt Robinson was an American professional baseball player who became the first Black American to play in Major League Baseball (MLB) in the modern era. Robinson broke the color line when he started at first base for the Brooklyn Dodgers on April 15, 1947. The Dodgers signing Robinson heralded the end of racial segregation in professional baseball, which had relegated black players to the Negro leagues since the 1880s.

The Kansas City Monarchs were the longest-running franchise in the history of baseball's Negro leagues. Operating in Kansas City, Missouri, and owned by J. L. Wilkinson, they were charter members of the Negro National League from 1920 to 1930. Wilkinson was the first white owner at the time of the establishment of the team. In 1930, the Monarchs became the first professional baseball team to use a portable lighting system which was transported from game to game in trucks to play games at night, five years before any Major League Baseball team did. The Monarchs won ten league championships before integration, and triumphed in the first Negro World Series in 1924. The Monarchs had only one season in which they did not have a winning record and produced more major league players than any other Negro league franchise. After relocating to Grand Rapids, Michigan, the team was disbanded in 1965.

The Brooklyn Dodgers were a Major League Baseball team founded in 1883 as the Brooklyn Grays. In 1884, it became a member of the American Association as the Brooklyn Atlantics before joining the National League in 1890. They remained in Brooklyn, New York, until 1957, after which the club moved to Los Angeles, California, where it continues its history as the Los Angeles Dodgers. The team moved west at the same time as its longtime rival, the New York Giants, moved to San Francisco in northern California as the San Francisco Giants.