On March 20, 2000 — 2000 – The new World Umpires Association agrees to consolidate all umpires as part of an interim agreement with the commissioner’s office. The umpires will merge into a single unit reporting directly to Major League Baseball this season, after being employed by either the National League or the American League since the latter’s creation in 1901.
Sources –
Baseball Reference March 20
SABR Games Project
National Pastime March 20
Retro Sheet
Replay The Game