home run king (1900)

“The Home-Run King” (Headline). Daily Reporter (Independence, KS), August 3, 1900, p3. (Refers to Buck Freeman, National League home run leader in 1899)

Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1930.  “If Hack Wilson is going to be the Home-Run King, New York will throw off the yoke of royalty and go republican.” (Howard Brubaker, The New Yorker, Sept. 6).