On May 18, 2000 — Mark McGwire hits three home runs and had a career-high seven RBI, leading the St. Louis Cardinals over the Philadelphia Phillies, 7 – 2, at Veterans Stadium. Curt Schilling (two) and Wayne Gomes (one) are his victims. The home runs move McGwire past Mickey Mantle into eighth place on the all-time career list with 539.
Source:
Baseball Reference May 18