For decades, baseball historians and fans have accepted it as gospel that Willie Mays collected 3,283 hits in his career, Bob Feller threw the only Opening Day no-hitter in baseball history and the top three batting averages of all time belonged to Ty Cobb (.366), Rogers Hornsby (.358) and “Shoeless” Joe Jackson (.356). To suggest otherwise was to provoke a bar fight — or at the very least a peaceful consulting of Google.

But on Wednesday, in a monumental change for the sport, Major League Baseball announced it was elevating the 1920-48 Negro Leagues to major league status, a move that not only seeks to right a cosmic wrong that has shadowed the game for a century — the segregation of baseball that famously ended when Jackie Robinson broke the color barrier in 1947 — but also forces a wholesale recalibration of its record book.

The “long overdue recognition,” as MLB called it in a news release, will add the names of some 3,400 Negro Leaguers from seven distinct leagues in the 1920s, 1930s and 1940s, along with all their accumulated statistics, to its official records. That means Negro League stars such as Josh Gibson, Oscar Charleston and James “Cool Papa” Bell — all of whom were inducted into the Baseball Hall of Fame in Cooperstown, N.Y., in the 1970s — will gain an additional designation denied to them during their lives: big leaguers.

“The Negro Leagues was a major league,” Bell, who died in 1991, told Gannett News Service in 1987. “They wouldn’t let us play in the white leagues, and we [were] great ballplayers in the Negro Leagues, so how can you say we [weren’t] major league?”

“All of us who love baseball have long known that the Negro Leagues produced many of our game’s best players, innovations and triumphs against a backdrop of injustice,” Commissioner Rob Manfred said in the statement. “We are now grateful to count the players of the Negro Leagues where they belong: as Major Leaguers within the official historical record.”

The move was the result of years of study by researchers from the Seamheads Negro League Database — who pored over newspaper clippings, scorebooks and other historical records to compile statistics — as well as research by the Baseball Hall of Fame, the Negro Leagues Baseball Museum in Kansas City, Mo., and other entities.

“In the minds of baseball fans worldwide,” Bob Kendrick, president of the Negro Leagues Museum, said in a statement, “this serves as historical validation for those who had been shunned from the Major Leagues and had the foresight and courage to create their own league that helped change the game and our country too.”

In effect, the move reverses the decision of MLB’s Special Baseball Records Committee — a five-person, all-White group commissioned in 1969 to codify the historical standards that define the major leagues — which bestowed big league status on six leagues (including the Union Association, which played its only season in 1884) but never even considered including the Negro Leagues.

“It is MLB’s view,” the league’s statement on Wednesday said, “that the Committee’s 1969 omission of the Negro Leagues from consideration was clearly an error that demands today’s designation.”

Wednesday’s announcement came near the end of a tumultuous year for MLB, in which, in addition to navigating a season amid a global pandemic, the sport, along with much of American society, grappled with significant issues regarding race and social justice. Teams and players sat out games this summer to protest police brutality, and earlier this week the Cleveland Indians announced plans to change their name after 105 years, following years of protests and pressure from Native American groups and others.

“The issues of inclusion and exclusion that the commissioner addressed today are really dramatic ones,” John Thorn, MLB’s official historian, said in a telephone interview. “We’re not merely focusing on stars like Gibson and Charleston but more than 3,400 men who seemingly had insignificant careers and who are now joined with their white peers in the record books. It’s big for a major institution [such as MLB] to admit publicly to a mistake and go about correcting it.”

As a practical matter, the change — once MLB and the Elias Sports Bureau conduct a review process to determine “the full scope of this designation’s ramifications on statistics and records” — is likely to upend segments of the sport’s cherished record book.

Mays, whose 3,283 career hits across a 22-year, Hall of Fame career rank 12th on the all-time list, could gain as many as 17 extra hits from the 1948 season, which he spent with the Birmingham Black Barons of the Negro American League. (Because 10 of those 1948 hits came in the playoffs, Mays’s career total might gain only an additional seven, depending on the results of the review process.)

Feller’s legendary Opening Day no-hitter in 1940 — long considered the only one of its kind in the sport’s history — will share that designation with Leon Day of the Negro National League’s Newark Eagles, who no-hit the Philadelphia Stars on Opening Day in 1946.

“He would have loved this. It would have meant the world to him,” Day’s widow, Geraldine, said in a telephone interview from her home in Catonsville, Md. Leon Day died in 1995 at age 78, four months before his induction into the Baseball Hall of Fame.

Since Negro League seasons were typically much shorter than MLB seasons, the sport’s career records for “counting” stats — such as Barry Bonds’s 762 home runs and Pete Rose’s 4,256 hits — are largely safe, if only because top Negro Leaguers are credited with having played between 1,000 and 1,600 career games, as opposed to, say, Rose’s 3,562.

For example, Gibson, who spent much of his career in Washington playing for the Homestead Grays and is considered the Negro Leagues’ most prolific slugger, is credited on his Hall of Fame plaque with hitting “almost 800 home runs.” Many of them, however, were on barnstorming tours and are not part of the official record, as determined by the Seamheads researchers, who credit him with only 238 in Negro League play — still most among Negro leaguers.

The all-time MLB rankings for “rate” statistics, such as batting average, on the other hand, could see a wholesale rewriting. Gibson’s career batting average of .365, for example, would rank second only to Cobb’s .366 and — along with Jud Wilson’s .359, Charleston’s .350 and Turkey Stearns’s .348 — would push Babe Ruth’s .342 out of the top 10. Gibson’s career slugging percentage of .690 would edge out Ruth’s .6897 as the highest in major league history.

Single-season stats also would be affected, with Gibson’s .441 batting average in 1943 supplanting Hugh Duffy’s .440 for the 1897 Boston Beaneaters of the National League as the highest in a single season in history. Ted Williams, who hit .406 for the Boston Red Sox in 1941, would lose his status as the last player to hit .400 in a single season.

Although most Negro League seasons featured between 50 and 70 games, MLB’s treatment of its own 2020 records as legitimate — despite playing a season that lasted just 60 games because of the coronavirus pandemic — proved to be illustrative in demonstrating the legitimacy of Negro League stats.

MLB is expected to use the same criteria to determine eligibility for single-season records as it currently uses for batting titles, with players required to have amassed 3.1 plate appearances per team game to qualify. A similar factor, one inning pitched per team game, is used for pitchers to determine eligibility for the ERA title.

Day’s .705 career winning percentage as a pitcher could put him in the top 10 all-time in the major leagues, just ahead of current Los Angeles Dodgers superstar Clayton Kershaw (.697).

“He didn’t talk much about himself or how good he was,” Day’s widow, Geraldine, said. “Other people talked about him like that, but he didn’t think words mattered that much. But he would be proud of this.”

This story has been updated.