Soriano belted his 53rd career leadoff homer on Wednesday to move into a tie with Craig Biggio for second all-time, trailing only Rickey Henderson, who hit 81.
Soriano connected off San Diego's Chris Young, hitting an 0-1 pitch that cleared the bleachers. It was Soriano's fourth leadoff blast this year and 21st as a Cubs player, breaking the old club mark of 20 set by Jimmy Ryan. Ryan played for the Cubs from 1885-1900.
Soriano has hit safely in nine of his last 10 games, and this is the fourth time in his career he's reached 10 homers by his 30th game.
Ryan Theriot followed Soriano by launching the first pitch he saw from Young into the bleachers in left-center for his fourth of the year, a career high. He added his fifth in the fourth inning for his second career two-homer game. He also did so Sept. 17, 2006, vs. Cincinnati. Theriot hit one home run last season, and his single-season high was three, done in both 2006 and '07. All of his home runs have come at Wrigley Field.
The Cubs hit back-to-back homers for the second time this season, but this was the first time they've done so to lead off a game since April 27, 2000, at Houston when Eric Young and Ricky Gutierrez did so off Jose Lima.
According to Elias Sports Bureau, it's the first time in San Diego franchise history that the Padres have served up consecutive homers to lead off a game.
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.