Mark David McGwire is a former professional baseball player who played the majority of his Major League career with the Oakland Athletics before finishing his career with the St. Louis Cardinals.

For his career, McGwire averaged a home run once every 10.61 at bats, the lowest at bats per home run ratio in baseball history . In 1987, he broke the single-season home run record for rookies, with 49. In 1998, McGwire broke the single-season home run record by hitting 70, but his mark was eclipsed by Barry Bonds with 73 in 2001.