On August 8, 1921
— Appearing as a pinch-hitter in the top of the ninth inning, Browns’ second baseman Luke Stuart hits a home run in his first major league at-bat. The 29 year-old rookie infielder, who is the first American Leaguer to accomplish the feat, strokes his only career round-tripper in a 16-5 loss to Washington at Griffith Stadium off future Hall of Famer Walter Johnson.

Source:
Baseball Reference August 8
National Pastime
Retro Sheet
Hall of Fame
SABR Games Project
Replay The Game