Why are MLB players wearing No. 42 jerseys today?

Cincinnati Reds - Today in Reds history 2007: Reds right fielder Ken Griffey Jr. sought permission from then-Commissioner Bud Selig and Robinson's widow, Rachel, to wear No. 42 on April 15. From

Red Sox to wear three uniforms in series versus Angels: What they mean

Do MLB players have to wear numbers on their uniforms? - Quora

Five Astros wear No. 21 on Roberto Clemente Day

Rubama: Coaches wanted their team of 7-year-olds to learn about Jackie Robinson. They got a lesson and wore No. 42 jerseys. – The Virginian-Pilot

MLB players honored to wear Jackie Robinson's No. 42

Minnesota Twins: Top 3 Players to wear Number 42 in Team History

Teams across MLB honor Jackie Robinson's 'eternal' impact

Dodgers manager Dave Roberts saving his sentimental side for Jackie Robinson Day – Orange County Register

Ken Griffey Jr. had Jackie Robinson Day idea