April 15th not only marks Jackie Robinson breaking the color barrier, but also the reintroduction of the mustache as worn by a baseball player on the field. In 1972 Reggie Jackson sported a mustache for the first time since 1914. A’s owner Charles Finley was inspired. Wanting to attract a younger audience, Finley offered $500 bonus to players to grow a mustache by Father’s Day. The team obliged, taking their scruff to a World Series championship against the Reds in a battle termed “the Hairs vs. the Squares.”

h/t Ken Singleton. More info here and here.