Foul Territory (1885)

“Mr. Irving does not consider it worthwhile to refute the statements about the hits over first and third, for a most excellent reason—he can’t. Facts are facts, and when a ball strikes a team six feet into foul territory, that ball is foul.” Fitchburg Sentinel, August 20, 1885, p2 (Letter from correspondent of the Gardner News to the Sentinel)

Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1908 (Brooklyn Daily Eagle, May 21; Edward J. Nichols).