In 1966, 23 year old Gibb became the first woman to run the Boston Marathon, effectively breaking the gender barrier for long distance running. Prior to the race, Gibb spent two years training for the competition, only to receive notice from race director Will Cloney that she was ineligible to compete. Cloney and the Amateur Athletic Union (AAU) felt that women were "not physiologically capable" of running such grueling distances. Undeterred, Gibb dressed in an oversized sweater and shorts and hid in the bushes near the starting line. Gibb later snuck in and joined the other runners, finishing the race in 3:21:40. Thirty years after her historic finish, the Boston Athletic Association retroactively recognized her as the women's winner in the 1966, 1967 and 1968 marathons. Gibb now works as a researcher, studying neurodegenerative diseases in San Diego and Boston.