Four-wheeled ambulances like the one pictured here were a major improvement over the two-wheeled versions issued in larger numbers early in the war. The latter were agonizingly uncomfortable for the wounded. Jonathan Letterman, medical director of the Army of the Potomac, brought the ambulances under the control of the medical department instead of the quartermaster corps, and manned them with soldiers trained for the job instead of with civilians, who tended to run away.
The greatest medical benefit of the war was the confirmation for doctors and the public that there was a connection between cleanliness and health, dirt and disease. This awareness, combined with the large number of doctors who gained valuable surgical experience, prepared the way for the rapid advances of the next thirty years as the causes of infection became known.