Dr. Copp was born in Salem, New Hampshire, and graduated from Dartmouth College (1881) and Harvard Medical School (1884). He joined the Taunton Massachusetts State Hospital, a hospital for epileptics, and was later chosen to oversee the construction of the Monson State Hospital, of which he later became the superintendent. In 1899, he was appointed Executive Officer of the Massachusetts State Board of Insanity. In 1908, he reported a need for a new kind of psychopathic hospital for research, education, and outpatient service, which led to the opening of the Boston Psychopathic Hospital in 1912. In 1909, he created the position of state pathologist, for which laboratory facilities were provided.
In 1911, he was appointed Physician-in-Chief and Superintendent of the Department of Mental Diseases at the Pennsylvania Hospital in Philadelphia. He rebuilt and remodeled the old buildings and supervised the building of the Institute of the Pennsylvania Hospital at 49th Street. He provided constructive leadership to the hospital and to American psychiatry, and he mentored several future APA presidents. He retired from the Pennsylvania Hospital in 1928.
Dr. Copp served as President of the American Medico-Psychological Association (1920–21).