From the Tattersall-McConnell Home Run Log:
http://members.sabr.org/members.cfm?a=rtl&rtl=enc&enc=hrl&pid=6135&yr=1911&hrv=b
09/02/1911 1 Bob Harmon (opposing pitcher for StL)
Btm 3; 1 outs; Bases Empty; Inside-the-Park HR; Day Game; Forbes Field
The home run is confirmed by the boxscore in this New York Times account:
O'TOOLE WINS AGAIN.
New York Times (1857-Current file); Sep 3, 1911; ProQuest Historical
Newspapers The New York Times (1851 - 2004) pg. C5
Rod Nelson