[2] He graduated from the University of Pennsylvania School of Medicine in 1898 and completed his internship at City Hospital in Newark, New Jersey.

[3] After completing his internship, McCoy joined the United States Public Health Service and was assigned to the U.S. Marine Hospital in San Francisco, California.

[4] While stationed in San Francisco, he became the director of the U.S. Plague Laboratory in 1908,[3] and during his time there he discovered, and later isolated the pathogen responsible for, a "plague-like disease of rodents", later dubbed tularemia.

Apart from his administrative role, he continued to conduct major medical studies on a variety of diseases, and advocated a combined field and laboratory approach to public health research.

[1] He resigned his position as director in early 1937, but remained with the Public Health Service to conduct a large, nationwide survey on leprosy.