The ball ricocheted off the mezzanine level and into the lower level of the left-field seats, where 28-year-old Davidson found the ball under a seat and "held on to it for dear life". He said he would return the historic memento to McGwire.
With the Maris family in attendance, McGwire turned on a 1-1 fastball from Cubs' starter Mike Morgan in the first inning, drilling it 430 feet just inside the left-field foul pole for his 61st homer of the season, equalling Maris's 1961 feat.
McGwire knew as soon as he hit the ball that he had equalled the record. "Yeah, I knew today just because it was a lot higher than yesterday," said McGwire, referring to his long foul ball on Sunday that narrowly missed being No 61. "As soon as it left my bat, I put my hands up and the ball probably hooked foul after the pole. But I knew at that time - what a feeling that was."
McGwire held both arms aloft as he watched the ball and started his home run trot, knowing it was gone. "It was almost like I was in awe," McGwire said. Cubs' Sammy Sosa, who has 58 homers this season, clapped quietly in the field.
McGwire tied the mark in the Cardinals' 144th game. He moved past Babe Ruth, who had 60 homers in 154 games in 1927, and has 19 games to break the single-season record. Maris hit his 61st homer on the final day of a 162-game season.
The Cardinals were due to play the Cubs again last night.