At the time of the American Civil War (1861-1865), a great deal was known about closed head injury and gunshot wounds to the head. Compression was differentiated from concussion, but localization of lesions was not precise. Ether and especially chloroform were used to provide anesthesia. Failure to understand how to prevent infection discouraged physicians from aggressive surgery. Manuals written to educate inexperienced doctors at the onset of the war provide an overview of the advice given by senior surgeons. The Union experiences in the treatment of head injury in the Civil War were discussed in the three surgical volumes of The Medical and Surgical History of the War of the Rebellion. Wounds were divided into incised and puncture wounds, blunt injuries, and gunshot wounds, which were analyzed separately. Because the patients were not stratified by severity of injury and because there was no neuroimaging, it is difficult to understand the clinical problems and the effectiveness of surgery. Almost immediately after the war, increased knowledge about cerebral localization and the development of antisepsis (and then asepsis) permitted the development of modern neurosurgery.