John Alexander Tyler died on September 1, 1883, aged thirty-five, while working as a mining engineer in New Mexico. His biography describes the fatal illness only as a fever. That historical description does not establish a precise modern diagnosis, and it should not be expanded into malaria, typhoid, or another infection without further evidence. His later career had included attempts to find engineering work in the American West and employment as a federal surveyor. These activities provide the setting in which the final fever occurred, but not a complete account of its symptoms, duration, or treatment. The yellow-fever quarantine that affected his naval service during the Civil War was decades earlier and is not proof of the cause of his death in 1883. The supported outline is a young engineer dying from an unspecified febrile illness in New Mexico, with his final attendants, last words, and exact medical mechanism left unverified.