Every year on April 15 — the anniversary of Jackie Robinson’s breaking the color barrier in 1947 — the baseball world spends a day reinforcing the importance of that legacy by celebrating Jackie Robinson Day. In 1997, Robinson’s No. 42 was retired across all of Major League Baseball in an unprecedented tribute. Today, teams across baseball will be sporting No. 42 jerseys to honor Robinson. Read more here.
No. 42 jerseys, Portland Sea Dogs Facebook graphic
No. 42 jerseys, Minnesota Twins Facebook photo
ballparkbiz.wordpress.com 
I was at a Great Lakes Loons game last night (April 15th). They never once mentioned it was Jackie Robinson Day, and this is a Dodgers affiliate. I thought it was pretty disgraceful