Farm Club (1896)

“Boston may get into line and organize a ‘farm’ club for the New England league.” The Inter Ocean [Chicago], January 12, 1896, p10.

Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1896. “[Dick] Padden, who has been playing with the Pittsburg farm club in the eastern league, has been called back” (The Boston Globe, July 15; Peter Morris).