Karen Stives earned her place in three-day eventing history when she rode her mother's big grey gelding, Ben Arthur, to win the individual silver medal in the 1984 Los Angeles Olympics. A single rail down in show jumping cost her the individual gold, but the pair's strong finish helped earn the team gold for the United States. Stives became the first woman ever to win an individual Olympic three-day event medal. Since then, 10 other women have duplicated the feat.

Stives is a New England rider who rose to the top of international competition through sheer diligence, hard work, and plenty of natural ability. Longtime friend and colleague Jim Wolf called her a "small package with a thousand-pound brain.” Stives was the USCTA Rider of Year in 1981, 1987, and 1988. She represented the U.S. in international three-day event competition on her wonderful Thoroughbred, The Saint, and rode for the U.S. at World Championships in Luhmühlen in 1982. It was there that Stives' mother, Lillian Mahoney, first saw an Irish-bred horse named Ben Arthur who had been leased from a British rider by a member of the New Zealand team. Mrs. Maloney purchased him for Karen after the competition, forming a partnership that would pay off two years later in Los Angeles.

Following her retirement from international competition, Stives served as an FEI judge and chair of the USET Three-Day Event Selectors' Committee for many years.