Willie McCovey extends his own National League record when he hits his 18th career grand slam in the third inning of the Giants’ 9-2 victory over Montreal at Olympic Stadium. The 39 year-old first baseman adds another round-tripper in the seventh, bringing his total to 484 major league home runs.

On August 1, 1977 — Willie McCovey extends his own National League record when he hits his 18th career grand slam in the third inning of the Giants’ 9-2 victory over Montreal at Olympic Stadium. The 39 year-old first baseman adds another round-tripper in the seventh, bringing his total to 484 major league home runs.

Source:
Baseball Reference August 1
National Pastime
Retro Sheet
Hall of Fame
SABR Games Project
Replay The Game