Tom O'Hara was the first native of the U.S. state of Illinois to break the four-minute barrier for the mile run. He accomplished this feat in 1963 when he ran the mile in 3:59.4. He also held the world record for fastest mile in indoor track, which was set when he ran the mile in 3:56.6 on February 13, 1964. He later beat that record on March 6 of the same year with a time of 3:56.4, a world record that stood for fourteen years.
At St. Ignatius College Prep High School, in Chicago, Illinois, O'Hara was a star runner on the school's cross country and track and field teams, often running--and winning--the quarter mile, half mile, mile, and mile relay in a single meet. He was a member of the Loyola University Chicago track, cross country, and indoor track teams. He was the individual champion of NCAA Division I men's cross country in 1962, and he participated in the 1500 m at the 1964 Summer Olympics, where he qualified for the semi-finals.