An analysis of the developments of field medicine during the American Civil War (1861-1865), focusing mainly on the Union Army. Disease was the largest cause of death during the war and had a more profound effects on its outcome that many of the battles themselves, representing more than two thirds of all deaths over the course of the war. This essay examines the watershed moment in American medicine that the Civil War represented and how changes in medicine were brought about and enacted, paying close attention to the development of medical infrastructure, competency, and efficiency, both during and after the war and how these factors would lead to a fundamental shift in medicine.