On July 29, 1915, At Forbes Field, Pittsburgh Pirates 41-year-old Honus Wagner becomes the oldest player in the history of the modern era to hit a grand slam when he connects off Robins hurler Jeff Pfeffer for a grand slam in the eighth inning. Wagnerâs home run, an inside-the-park shot, helps Pittsburgh to an 8-2 victory over Brooklyn. Wagnerâs record will stand until 1985, when 42-year-old Tony Perez belts a grand slam.