During the Civil War, the most common way of treating wounds was amputation to the affected area. Most surgeons or doctors did not even know how to treat a gunshot wound. 75% of amputees did survive. For the most part they were given prosthetic limbs.
Common places like houses, churches, or barns were used as hospitals. These places were marked with a green "H" on a yellow flag. Doctors and nurses saw patients by the thousands, sometimes using unconventional ways to treat as many people as they could.
Chloroform was the most common anesthetic, used in 75% of operations. In a sample of 8,900 uses of anesthesia, only 43 deaths were attributed to the anesthetic, a remarkable mortality rate of 0.4%. Anesthesia was usually administered by the open-drop technique. The anesthetic was applied to a cloth held over the patient's mouth and nose and was withdrawn after the patient was unconscious. Sometimes they would not use any anesthetic giving the patient something like a belt to bite on while the surgeon operated.
One famous physician was Jonathan Letterman, otherwise known as "The Father Of Battlefield Medicine." Jonathan Letterman saved thousands of lives by establishing ambulance corps, a prioritizing system based on the wound of a soldier and the likelihood of survival, a system of treating patients after evacuation. This system included the steps of constructing a field-dressing station next to the battlefield to quickly dress wounds and stop bleeding; a field hospital close by, usually in homes or barns, where emergency surgery could be performed; and a large hospital located away from the battlefield that would provide long-term treatment.
“I often wondered whether, had I been confronted with the primitive system which Letterman fell heir to at the beginning of the Civil War, I could have developed as good an organization as he did. I doubt it. There was not a day during World War II that I did not thank God for Jonathan Letterman.” —Major General Paul Hawley, Chief Surgeon of the European Theater in WWII