PITTSBURGH -- The Chicago Cubs stole eight bases -- their most in a game in more than 100 years -- and had 21 hits on the way to an 18-8 victory over the Pittsburgh Pirates on Monday night.

Dansby Swanson broke the game open with a grand slam off Domingo German in the sixth inning to push the Cubs' lead to 9-2.

It was the third grand slam of the shortstop's nine-year career -- and second this season. He also homered with the bases loaded on April 24 against Houston rookie Spencer Arrighetti.

The Cubs last had eight steals in 1913. Their last game with more was 10 steals in 1907 against the Giants, according to ESPN Stats & Information research.

Rookie center fielder Pete Crow-Armstrong led the way with three stolen bases as the Cubs won for the seventh time in 10 games. That raised his season total to 26 in 93 games. Crow-Armstrong has only been caught once this year.

"I think we've done a good job all year of going into it with the mindset of being aggressive on the bases," Crow-Armstrong said. "Against these guys, we've had a pretty good plan and you saw it today because guys were very aggressive."

Ian Happ added two steals and Nico Hoerner, Cody Bellinger and Seiya Suzuki had one each. All eight steals came in eight attempts against catcher Yasmani Grandal. Starter Mitch Keller was on the mound for seven steals during his four innings.

Chicago entered the game eighth in the major leagues in stolen bases with 112.

"There wasn't a lot that went right tonight, so I don't know if I would highlight the stolen bases as being the issue," Pirates manager Derek Shelton said. "But, yeah, we've got to do a better job of holding runners."

Miguel Amaya had a career-high four hits and four RBIs for the Cubs. His double knocked in the first two runs in an eight-run sixth inning to make it 5-2 before Suzuki hit a run-scoring single, Hoerner drew a bases-loaded walk from German and Swanson hit his slam.

Amaya is 12 for 18 with three homers and 10 RBIs in his last five games.

Suzuki also had four of the Cubs' 21 hits and Crow-Armstrong added three as Chicago set a season-high in runs. Bellinger and Isaac Paredes had two hits and two RBIs each with Paredes belting a solo home run in the eighth off Brady Feigl to extend the lead to 12-4.

"Having depth in the lineup one through nine is a big deal in the game today," Swanson said. "Everyone's contributing right now and there's evidence of that over the last month, month and a half."

The Cubs are 15-8 since July 31.

The Associated Press contributed to this story.