42, besides being the key to life, was also Jackie Robinson's number. Today is Jackie Robinson Day for Major League Baseball, where every player wears the number 42. Normally, the only player to wear 42 is Mariano Rivera - and he will be the last to do so. MLB retired #42 in 1997, and Rivera is the last active player who was wearing 42 at that time.
Flip Flop Fly Ball put together a cool graphic in commemoration of today, showing the last player on each team to wear #42. Go check it out - and also Go Cubs!