 July 18, 1962, two of the greats. Harmon Killebrew and then Bob Allison would both hit Grand Slams, the first to hit two Grand Slams in one inning for an American League club in 1962. In the 1987 World Series, the Twins became the first team to hit two Grand Slams in World Series history in two different games when Dan Gladden and Kent Herbeck