On October 16, 1846 dentist William T. G. Morton successfully demonstrated at the Massachusetts General Hospital that ether could prevent the pain of surgery. For decades afterwards, the administration of anesthesia in the United States was generally relegated to dentists, medical students, junior surgical trainees, or even nonmedical personnel. It was not until the end of the 19th century that a few pioneering physicians began devoting their careers to administering anesthesia to patients, studying ways to make it safer and more effective, and teaching others about its use. One of these individuals was Freeman Allen, who was appointed the first physician anesthetist to the medical staff at the Massachusetts General Hospital and several other major hospitals in Boston. We describe this remarkable man, his contributions to the early development of anesthesiology as a medical specialty, and the true cause of his untimely death.