1929 – Trying to curb the hitters, National League president John Heydler orders umpires to rub up new balls before each game to remove the gloss.

On July 18, 1929 — 1929 – Trying to curb the hitters, National League president John Heydler orders umpires to rub up new balls before each game to remove the gloss.

Source:
Baseball Reference July 18