Callahan graduated from high school in 1950. The University of Illinois was his college choice, which he attended on an academic scholarship he won on a competitive examination. Dentistry became his chosen field so he attended the University of Illinois College of Dentistry in Chicago for four years and graduated in 1957. The U.S. Military was on everyone's agenda in those days so he served as a dentist in the Army for three years including a year in Korea. After military service Dr. Callahan was one of the ten out of six-hundred applicants who were accepted into orthodontic training at Northw...