Mark McGwire Sets Rookie HR Record On this day, in 1989 Oakland's Mark McGwire set a rookie HR record at 39, he ended his rookie season in the MLB with 49 home runs. August 14, 1989 Sport: Baseball Trivia What Are the Five Events That Make Up the Modern Olympic Pentathon? Which Nations Won the Gold, Silver and Bronze Medals the Last Time Baseball Was an Olympic Sport? sports in this article Baseball tags in this article Fan On This Day SportsEngine