why is the mlb wearing 21 today

Major League Baseball (MLB) players, managers, coaches, and umpires are wearing number 21 today to honor Roberto Clemente because it is Roberto Clemente Day, celebrated on September 15th. MLB commemorates Clemente, a Hall of Famer and humanitarian, who wore No. 21 throughout his career with the Pittsburgh Pirates. As part of the celebration, all MLB personnel wear a white "21" patch on their uniforms, and players of Puerto Rican heritage, past Clemente Award winners, and nominees for the award may wear No. 21 as their uniform number during games. This tribute honors Clemente's legacy as a great player and humanitarian who died delivering earthquake relief supplies in 1972. The Pirates also wear No. 21 across their roster in recognition of Clemente, who spent his entire career with that team.