On August 6, 1890 — John Reilly becomes the first major leaguer to hit for the cycle in different leagues when the Reds, who moved to the National League this season, beat Pittsburgh at League Park, 16-3. The Cincinnati first baseman hit for two cycles in 1883, also a first, when the team played in the American Association and were known as the Red Stockings.

Source:
Baseball Reference August 6
National Pastime
Retro Sheet
Hall of Fame
SABR Games Project
Replay The Game