OTD (On This Day) in 1963, Minnesota Twins sluggers Bob Allison and Harmon Killebrew become the first teammates in MLB history to hit grand slams in the same inning. Allison hits a baseball loaded home run off Cleveland starter Barry Latman in the 1st inning and Killebrew hits his grand slam 8 batters later in the 1st inning off Jim Perry, who came in to relieve Latman. The Twins would score 11 runs in the 1st against the Indians on their way to a 14-3 victory at Metropolitan Stadium in Bloomington, MN. The Old Met was torn down in 1985 and the Mall of America was built on the site in 1989, opening in 1992.
Both Allison and Killebrew played for the 1956 Charlotte Hornets of the South Atlantic League. Allison would hit 12 HRs in 344 ABs for the Hornets and Killebrew would contribute 15 in 249 ABs.
Box score of record setting game: https://www.baseball-reference.com/boxes/MIN/MIN196207180.shtml