On August 5, 1974 — 1974 – In the top of the 9th inning at Dodger Stadium, during an ABC Monday Night telecast of the Reds-Dodger game, Alex Stein, 19, and his tiny Whippet, Ashley, dash onto the field and begin lofting spectacular Frisbee tosses. The crowd roars and the two are caught on NBC cameras, initiating a Frisbee craze. Stein, who snuck his dog into the stadium, is arrested when he leaves the field.

Source:
Baseball Reference August 5
National Pastime
Retro Sheet
Hall of Fame
SABR Games Project
Replay The Game