Why Jackie Robinson Is Honored by MLB on April 15

April 15 is a big day for MLB teams, players and fans. Every baseball team playing today will wear No. 42 to honor Jackie Robinson who wore the same number when he was a member of the Brooklyn Dodgers. It’s the only time players can wear No. 42 as it’s retired throughout MLB. But why is April 15, also known as Jackie Robinson Day a special day for baseball?

April 15 was that day in 1947 when Robinson made his MLB debut, becoming the first African American to play in the big leagues. It marked the beginning of a new era for baseball as Black players had to play in the Negro Leagues at the time due to racial segregation. Robinson was a member of the Dodgers from 1947-1956 and was named to the All-Star team six times. He helped the Dodgers win the World Series in 1955 and was named NL MVP in 1949.

“It was the most eagerly anticipated debut in the annals of the National Pastime,” authors Robert Lipsyte and Pete Levine wrote per the Baseball Hall of Fame’s website. “It represented both the dream and the fear of equal opportunity, and it would change forever the complexion of the game and the attitudes of Americans.”

Robinson made an impact was huge as it paved the way for other legends such as Williams Mays, Hank Aaron, and Ken Griffey Jr. Today, more than 100 players are donating their April 15 game-day salaries to support the Players Alliance, which works to promote Black participation in baseball as well as a more diverse future in the sport.

“On April 15, we honor Jackie Robinson as the first player to break the color barrier, a reminder there is still much work to be done in our game,” Alliance president and former major leaguer Curtis Granderson said in that same statement per CBS Sports. “As The Players Alliance seeks to bridge the gap of racial inequity in baseball, we’re encouraging players, on this date especially, to consider supporting the Alliance and our efforts to continue Jackie’s legacy of breaking barriers.”