Dr. McGraw worked in private practice from 1935 to 1936 in Pennsylvania as a general practitioner and surgeon. In 1937, on his 25th birthday, he entered military service as a first lieutenant in the U.S. Army. By 1942, within five years of joining the army, first lieutenant McGraw had advanced to the rank of colonel. In 1944, Colonel McGraw was reassigned to the position of Assistant Commandant of the AAF School of Aviation Medicine at Randolph Field (San Antonio) Texas.