Today, Major League Baseball honors one of the most influential ballplayers ever — Jackie Robinson.

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Nearly 80 years ago, Robinson broke down barriers and ushered in a new era in baseball, and each year on April 15, MLB celebrates “Jackie Robinson Day,” along with millions of sports fans who appreciate what he accomplished.

But what is Jackie Robinson Day? Why does MLB celebrate it? Why is it so important?

With MLB action back on NBC and Peacock this season, here’s everything you need to know about Jackie Robinson Day and the fascinating legacy of one of the most trailblazing stars ever to play the game.

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Why is April 15 Jackie Robinson Day in Major League Baseball?

When answering, “When is Jackie Robinson Day?” it’s best to turn back the clock nearly 80 years.

On April 15, 1947, at the age of 28, Robinson became the first African American to play in Major League Baseball’s modern era, making his big league debut for the Brooklyn Dodgers against the Boston Braves before a crowd of over 26,000 fans at the iconic Ebbets Field. The team had called him up from the minors just five days earlier.

More than half of the fans in attendance that day — approximately 14,000 — were Black.

From that point forward, Black athletes were no longer relegated to the Negro leagues. And while Robinson still encountered racism from players, coaches, and fans throughout his MLB career, his willingness to change the course of American history has been immortalized by sports fans everywhere.

In honor of Robinson breaking the color barrier, all MLB players wear #42 on Jackie Robinson Day. This year marks the 79th anniversary of that incredible moment.

In 1997, Robinson’s number was universally retired throughout all of MLB — no player can wear that number except on this day — and is prominently featured in every stadium. Appropriately, #42 is the first number to be retired throughout an entire professional sport.

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Why was Jackie Robinson important to MLB?

Before Robinson took the field for the Brooklyn Dodgers on that fateful day in 1947, segregation was running rampant through MLB — and society in general. Robinson’s inclusion in that day’s Dodger lineup signaled the end of racial segregation in baseball.

Until April 15, Black athletes were forced to play in designated “Negro leagues” and were effectively banned from participating in MLB games.

In 1945, Robinson began his career in the Negro leagues, playing 47 games for the Kansas City Monarchs before joining the minor leagues the following year.

Effectively, Robinson ushered in a new era of true player empowerment. Thanks to the star, Black men around the country could fulfill their dreams of playing in a Major League Baseball stadium.

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Who did Jackie Robinson play for?

Robinson played for the Brooklyn Dodgers from 1947 until 1956.

In his 11 professional seasons (including his time with the Royals), Robinson played in 1418 games and boasted a .313 batting average. He was the National League’s MVP in 1949 and helped lead the Dodgers to the 1955 World Series Championship over the New York Yankees.

Today, the spirit of Robinson lives on — especially in his granddaughter, Sonya Pankey Robinson. On April 14, the UCLA Bruins college baseball team wore commemorative uniforms specially designed by Pankey Robinson.

“His story doesn’t end here,” she said while addressing the team. “You guys are the future, and I hope you use his story as a guide for your future mission. I hope you wear the jersey with pride and let it inspire you to build your own legacy that opens doors and creates opportunities for those to follow.”