On June 27, 1977, Willie McCovey of the San Francisco Giants hits two home runs in one inning and becomes the all-time National League leader with 17 career grand slams. McCovey homered of Jack Billingham with one out made the score 8-4, 9 batters later McCovey hits a grandslam off reliever Joe Hoerner, he entered the 6th with two outs, the sacks full, and the Reds holding a 7 – 6 lead. He hits two batters, then serves up the slam to McCovey, giving the Giants a 13-8 lead. The Giants defeat the Cincinnati Reds, 14-9.

Willie McCovey becomes the first major leaguer to hit two homers in one inning twice in his career. The Giants’ first baseman first accomplished the feat on 4/12/73. Andre Dawson, in 1978 and 1986, will also clout two round-trippers in an inning twice.