On May 8, 2000 — Mark McGwire of the St. Louis Cardinals hits his 12th home run of the season, against the San Francisco Giants. The homer ties “Big Mac” with Jimmie Foxx for ninth place on the all-time list with 534 career homers. McGwire needs just two taters to catch number eight on the list, Mickey Mantle, at 536.

Source:
Baseball Reference May 8