MLB remembers the official founding of the Negro Leagues in 1920 today:

The Negro Leagues are getting the kind of recognition they deserve today. All Major League clubs will celebrate the centennial of the founding of the Negro National League — the first structured Negro League that lasted for an extended period — with all players, managers, coaches and umpires wearing a Negro Leagues 100th anniversary logo patch on their uniforms during today’s games. The logo, a derivative of the official logo created by the Negro Leagues Baseball Museum, also will be featured on base jewels and lineup cards.

MLB.com

Much more information on the events happening throughout the game and the country at the link.