J. (John) Charnley McKinley earned the doctor of medicine degree from the University of Minnesota in 1919. Continuing as a teaching fellow, in 1921 he received a doctor of philosophy degree in nervous and mental diseases.  His teaching and research abilities were quite evident and, with Dr. Hamilton's hearty endorsement, he then became assistant professor of nervous and mental diseases. He was the first full-time faculty member in the field of neurology. In 1925, he was advanced to associate professor.  In 1928, he received a Guggenheim Fellowship and studied neuropathology and neurology at the Universities of Breslau and Munich , Germany . Upon his return to the Medical School in 1929, he became professor of nervous and mental diseases.  In 1934, he was made administrative head of the Department of Medicine. He was president of the Central Neuropsychiatric Association in 1938.  He was a director of the American Board of Psychiatry and Neurology from 1941 to 1945.   

Dr. McKinley did extensive research on muscle tonus and in poliomyelitis. He compounded a vaccine for active immunization against poliomyelitis; and offered a proposal of wholesale passive immunization against poliomyelitis epidemics. He studied the mid-brain nuclei in post encephalitic paralysis agitans and did meticulous stains and cell counts of these areas. 

A methodical teacher and author, McKinley was precise in his lecturing and writing. His scientific watchwords were accuracy and honesty. Early in his career in 1915, he prepared Sensory Nerve Topography charts, showing the segmental and radicular distributions, and companion Motor Function charts. These charts, which he carefully constructed from a composite of all the anatomy and related texts in print, have been reproduced in numerous standard text-books and are still recognized as the most usable and accurate neurologic information of its kind extant. In 1939, he edited An Outline of Neuropsychiatry, A compendium and ready reference book for student and practitioner.  This Outline went through four editions, the last one in 1944, and was widely used for many years.  Dr. McKinley was convinced that most disasters in politics, crime and the like are due to mental disorders that should be detected before catastrophe occurred.  He was influential in the enactment of the Minnesota Psychopathic Personality Law. Inasmuch as no device was available for quickly screening such personalities from any group of individuals, in collaboration with Dr. Starke R. Hathaway, he developed the Minnesota Multiphasic Personality Inventory. This is a psychometric device for the more objective evaluation of personality, especially in psychiatric terms. An account was first published in 1942 and because of the overwhelming demand on the local facilities for manufacture; it was released to the Psychological Corporation in New York for manufacture and distribution.  It has been used routinely by hundreds of private clinics and individual doctors as well as large organizations. In 1942, McKinley was commissioned to edit a three volume text on Clinical Neurology, planned to be a complete treatise on the subject, and he arranged with 30 nationally known neurologists to contribute chapters. The edition was well under way when it was stayed by-situations incident to World War II. Dr. McKinley was disabled by a stroke in 1946 and was succeeded by Dr. A.B. Baker.