Dr. Gerty was born in Chicago, Illinois, received his M.D. (1921) from Loyola University Medical School, interned at Cook County Hospital, and was assigned to the County Psychopathic Hospital. In 1922, he was elected County Physician and Medical Superintendent of the Cook County Psychopathic Hospital (1924–2021).
In 1923, Dr. Gerty began teaching psychiatry at Loyola, and in 1930, he was appointed to the chairmanship of the department. In 1941, he was elected Professor and Chairman of the Department of Psychiatry at the University of Illinois School of Medicine, a post he retained until 1960. He was Director of the Psychopathic Division of the Illinois Psychiatry and Neurology Division of the Department (1941–60), Director of the Department of Public Welfare, and Department of Mental Health (1961–63). He was on the staff of a number of Chicago hospitals and councils, including the Director of the Department of Mental Health for Illinois (1961–63), a member of the American Board of Psychiatry and Neurology (1952–60) and its President (1959–60), and a trustee of the Chicago Psychoanalytic Institute (1945–56).
Dr. Gerty was a Lt. Cmdr. in the U.S. Naval Reserves (1933–51), received honorary degrees from Loyola University (1957) and the University of Illinois (1976),
Dr. Gerty served as President of the American Psychiatric Association from 1958–59.