Today is Jackie Robinson Day.

Major League Baseball will celebrate Jackie Robinson Day today (April 15th), with all players, managers, coaches and umpires to wear Robinson’s Number 42. The date marks the anniversary of when the Hall of Famer debuted with the Brooklyn Dodgers in 1947, breaking baseball’s color line. A video called, “Thank You, Jackie” will be shown at all ballparks, and more than 100 players will donate either all of part of their game-day salaries to support The Players Alliance, an organization of current and former MLB players advocating for Black representation in baseball.