But on July 31, the day of the Trade Deadline, a slumping Cardinals team shipped a trio of pitchers -- T.J. Mathews, Eric Ludwick and Blake Stein -- to Oakland for the 33-year-old slugger. Then, McGwire turned heads by re-signing with the club for four more seasons, attributing much of his decision to a desire to reunite with Cardinals skipper Tony La Russa and general manager Walt Jocketty, both formerly with the Athletics.
Despite his 4 1/2-season tenure in St. Louis, the former first baseman left his mark on the franchise with record-breaking 1998 and three All-Star campaigns. It was enough to earn him consideration for the new Cardinals Hall of Fame gallery located in the recently opened Ballpark Village.
From now until April 22, fans can vote at Cardinals.com/HOF for up to two of the eight modern legends -- McGwire, Matt Morris, Keith Hernandez, Jim Edmonds, Bob Forsch, Willie McGee, Ted Simmons and Joe Torre.
The top two vote-getters will be enshrined during an Aug. 16 ceremony at Ballpark Village, joining the 22 Cards who received automatic induction because they are either already in the National Baseball Hall of Fame or have had their number retired by the organization.
In his second season in St. Louis, McGwire and Cubs right fielder Sammy Sosa captivated the nation in a race to break Roger Maris' single-season home record, set at 61 in 1961.
"The whole season was, I would have to say, very stressful," said McGwire, now the Dodgers' hitting coach. "I don't think any athlete at that time had to deal with the individual achievements where the country follows on a daily basis. ... We've had some athletes that carried teams or had some team things, Michael Jordan, Magic Johnson, you could go down the line, but [not] as far as an individual accomplishment where the country really took over."
McGwire and Sosa, as well as Seattle's Ken Griffey Jr., hit homer after homer at a record pace. On Sept. 7, McGwire matched Maris' record 61 homers. Though Griffey had fallen behind with 50, Sosa was still within reach at 58.
The next day, hours before he would get his first crack at breaking the record, McGwire remembers it being very calm, a far cry from the media frenzy that followed him and Sosa the entire season. By the time he stepped up to the plate in the bottom of the fourth inning, a thought passed through his mind: "The old saying, the calm before the storm."
He lined his first pitch from Chicago's Steve Trachsel -- a sinker, as McGwire recalls it -- just beyond the left-field wall, becoming the new single-season home run king. And it was only fitting that No. 62 came at home against Sosa's Cubs.
"Sammy pushed me all year," McGwire said. "At that time, in Sammy's career, people knew that he hit home runs, but he didn't start really hitting them until I think it was late May and June. And then he came on, and he came on strong.
"It made me go into another level as far as my mindset, because I was the one that broke the record. But, you know, I still had a lot of games left to play where Sammy could have actually finished the season leading and holding the record."
A fact not lost on McGwire as he went into the final two days of the regular season tied with Sosa at 66 home runs apiece. McGwire would smash four more long balls in the Cardinals' last two contests, out-dueling Sosa to set the record at 70, which would hold for just three seasons until Barry Bonds' 73-homer campaign in 2001.
The 12-time All-Star spent two more seasons in St. Louis, retiring as a Cardinal in 2001. His impressive 16-year resume earned him a place on the National Baseball Hall of Fame ballot in 2007, where he has remained for eight years, his Cooperstown candidacy divisive due to his 2010 admission of PED use.
McGwire returned to St. Louis in 2010, serving as the club's hitting coach for three seasons. In 2013, the allure of living at home with his wife and five young children proved too much as he accepted the same position with the Los Angeles Dodgers.
Though his St. Louis coaching career was, like his playing career, short-lived, McGwire still managed to once again leave his mark upon the organization. He still talks with great pride of his former players, many of whom credit McGwire for much of their success at the plate.
"It was a very difficult decision to leave St. Louis," McGwire said. "I'm in a really great organization with the Dodgers. I'm very happy."