Holliday jumped a 1-1 slider from Gallardo that was up and over the plate, and deposited it just over the wall in right field in the fifth inning. The shot scored Albert Pujols, who had singled, and gave the Cardinals valuable insurance on their way to an 8-4 win and a sweep of the Brewers.
It was one of seven homers hit that accounted for all of the scoring in the game between the two teams. Pujols went deep twice, including his 12th career grand slam.
Holliday moved into a tie for 296th place on the all-time list with Jason Bay, Bill Freehan, Oscar Gamble and Don Mincher. It was his 61st home run as a Cardinal, following 128 with the Rockies and 11 with Oakland.
The homer was his 20th of the season, marking his sixth straight season reaching that plateau.
Matthew Leach is a reporter for MLB.com. Read his blog, Obviously, You're Not a Golfer and follow him on Twitter at @MatthewHLeach. This story was not subject to the approval of Major League Baseball or its clubs.