It has been more than 42 years since Jackie Robinson left us.
The number is everywhere you look.
It is memorialized beyond outfield walls at 30 Major League ballparks. It was worn Wednesday by every single player in the big leagues, as Jackie Robinson Day was celebrated all over, including by Robinson's former Dodgers club as it hosted Seattle in a special Civil Rights Game to honor this occasion.
On April 15, 1947, Robinson took his position at first base for the Brooklyn Dodgers at Ebbets Field and became the first African-American player to break the game's color barrier.
Video: Dodgers set to host 2015 Civil Rights Game
The door was swung open. Many of the greatest athletes in all sports today owe their success in part to what Robinson did 68 years ago and how he did it. His act was also among the key forces in a civil rights movement.
"It was the most eagerly anticipated debut in the annals of the national pastime," Robert Lipsyte and Pete Levine wrote in "Idols of the Game." "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."
MLB announced in 1997 that to mark the 50th anniversary of that landmark event in the American timeline, all clubs would retire the No. 42. Any active players still wearing it would be allowed to do so until retirement, and none remain due to the subsequent departures of Mo Vaughn and Mariano Rivera.
Video: Players, managers talk playing on Jackie Robinson Day
The first Jackie Robinson Day was officially recognized on April 15, 2004. Bud Selig, Commissioner at that time, said of that new league-wide recognition: "We are further ensuring that the incredible contributions and sacrifices he made -- for baseball and society -- will not be forgotten."
They are not forgotten. In 2007, players, managers and coaches were invited to wear No. 42 on Jackie Robinson Day in tribute, and Ken Griffey Jr. obliged. It was the catalyst for a tradition.
:: Jackie Robinson Day | Civil Rights Game ::
"It's a great day," said Rangers first baseman Prince Fielder, who wore 42 in an afternoon home game against the Angels. "Obviously, Jackie is the main reason why I'm able to play the game today. It's definitely a great day and it's definitely cool to wear No. 42 for one day a year."
"Jackie meant so much to the game of baseball and obviously to minorities," Mariners manager Lloyd McClendon said. "He's the main reason I'm sitting here today, because he opened doors that weren't open. It took a lot of courage."
It is not about one day out of 365. It is a reminder of the courage by Robinson and foresight by former Dodgers general manager Branch Rickey to change a game and society.
On 2015 Opening Day active rosters, the percentage of total Major Leaguers who are black, African-American or African-Canadian was 8.26 percent -- consistent with Opening Day figures over the past few years. More than 65 percent of these players are 30 years old or younger.
Video: MLB and fans everywhere celebrate Jackie Robinson Day
That number was affected by Spring Training injuries to such established Major Leaguers as Melvin Upton of the Padres, Coco Crisp of the A's, Domonic Brown and Mario Hollands of the Phillies, Marcus Stroman of the Blue Jays and Denard Span of the Nationals.
Video: Commissioner Selig on Civil Rights Game festivities
The highest percentage of African-Americans playing in the Majors was 19 percent in 1986, according to Mark Armour from the Society of American Baseball Research. Armour said the previously reported peak of 27 percent in the mid-1970s was mischaracterized because it included dark-skinned players from Latin American countries.
Efforts to increase those numbers are a year-round endeavor throughout MLB, which recently appointed longtime baseball executive and former Angels GM Tony Reagins as senior vice president for youth programs. In his role, Reagins oversees MLB's expanded focus on youth baseball participation, including Reviving Baseball in Inner Cities (RBI) and the MLB Urban Youth Academies, and he serves as the main liaison between MLB and all baseball (youth and amateur) organizations.
RBI has served more than 2 million young people since its inception. The program has grown by nearly 80 percent since 2009, when RBI expanded to include ages 5-12; it was previously only available to the 13-18 age group. It now serves about 225,000 kids in 300 programs throughout the U.S., Puerto Rico, the Dominican Republic, Curacao and Venezuela.
Video: BAL@HOU: Robinson on importance of Civil Rights Game
Collectively, the four MLB Youth Academies annually serve more than 7,000 young men and women. In Houston, the Jackie Robinson Day celebration will also include young ballplayers from the Astros Urban Youth Academy taking the field with Astros players prior to start of the 8:10 p.m. ET game against Oakland. More than 500 Urban Youth Academy members will be in attendance, compliments of the Astros.
The Civil Rights Game, entering its ninth season, was created to honor Robinson's legacy, along with the countless other trailblazers who helped spark a revolution of societal change. Its date was moved up this year to coincide with Jackie Robinson Day, given the team hosting it.
Magic Johnson and Dolores Huerta were honored with Beacon Awards at the annual luncheon before the Civil Rights Game, a 5-2 Dodgers win.
Johnson, one of the greatest players in National Basketball Association history, is a successful businessman and philanthropist and a partner in the Dodgers' ownership group. Huerta, 85, an early member of United Farm Workers, is a famed labor leader and civil rights activist who was previously awarded the Presidential Medal of Freedom.
A roundtable discussion about baseball and the civil rights movement was also held as part of the Civil Rights Game festivities, an event moderated by Harvard Law School professor Charles Ogletree. Sharon Robinson, Jackie's daughter, was an important part of the panel discussion.
For progress to happen, one first has to know Jackie Robinson's story. Making sure the youngest generation knows about it should be a priority.
"It's as clear now as it was then that Jackie Robinson was the right man for the right job -- intelligent, educated -- I think that's what we needed," Hank Aaron wrote in the introduction to Robinson's autobiography, "I Never Had It Made."
"There were so many temptations put before him. He was a man on trial -- not only on the field. But off the field as well, and he had the skills to survive and transcend this ordeal."
Jack Roosevelt Robinson died of a heart attack at the age of 53 on Oct. 24, 1972. The day created in his honor is a time to remember his fight and to appreciate what it means today.
Mark Newman is enterprise editor of MLB.com. Read and join other baseball fans on his MLB.com community blog.
This story was not subject to the approval of Major League Baseball or its clubs.