On April 15, 1947, more than 26,000 spectators at Brooklyn's Ebbets Field witnessed history as Jackie Robinson became the first Black player on a modern-era major league baseball team. (Three Black players played in the major leagues briefly in the 19th century before the color line was fully established.) Robinson endured racist resistance throughout his first season with the Brooklyn Dodgers, but the national pastime's color barrier was broken, and other players followed him within months. In 1997, Major League Baseball retired Robinson's number, 42, across all teams, and in 2004 it began the annual April 15 observance of Jackie Robinson Day. This photo shows Robinson signing autographs for fans at spring training in the Dominican Republic the year after his debut.