Participating in the “Tip Your Cap” campaign, which was organized by Negro Leagues Baseball Museum president Bob Kendrick and started two weeks ago, Barack Obama, George W. Bush, Bill Clinton and Jimmy Carter on Monday shared their messages of support.

“That alone validates this project,” Kendrick said Monday of the former presidents’ participation (via MLB.com). “It many ways, it validates the Negro Leagues Baseball Museum. Naturally, we feel that is a coup. It’s the ultimate show of respect of what this museum represents, not only here in Kansas City, but to our nation.”

The “Tipping Your Cap” campaign’s site calls the participation of Obama, Bush, Clinton and Carter “an unprecedented American salute for the men and women who were denied the chance to play in the Major Leagues because of the color of their skin but continued to strive and excel and play ball.”

Basketball legend Michael Jordan is among the celebrities who also have tipped their caps to acknowledge the 100-year anniversary of the formation of the Negro Leagues.