Analysis of information sources in references of the Wikipedia article "List of Major League Baseball single-game grand slam leaders" in English language version.
Bill Mueller...became the only player to hit grand slams from both sides of the plate in the same game.
[Northrup] drilled Fisher's first offering over the right field fence, then unloaded another first-pitch grand slam off southpaw Hill Rohr in the sixth...
Bill Mueller...became the only player to hit grand slams from both sides of the plate in the same game.