3. 56,000 (or about 13½%).
The following is excerpted from Alan Marsh, Cultural Resources Specialist, “POW’s in American History: A Synopsis,” 1998, Andersonville [Georgia] National Historic Site, National Park Service:
During the Civil War, an estimated 194,000 Union soldiers and 214,000 Confederate soldiers became prisoners of war, more than in any other conflict in the history of the country. Approximately 30,000 Union soldiers died in Confederate prisons while the death rate was almost as bad in the North with approximately 26,000 Confederate soldiers dying in Union prisoner of war camps. Since both sides predicted a short war, neither prepared for large numbers of POWs during the four years of conflict. As prisoners were taken, commanders usually worked out exchanges among themselves. Soon an exchange system was accepted by both governments, but failed to work due to a variety of disagreements that arose. The number of prisoners of war increased and prison facilities on both sides became severely overcrowded. Mismanagement, lack of adequate planning, retaliation and many other factors led to suffering by prisoners on each side. By the end of the war, camps such as Andersonville suffered from a lack of supplies and experienced extremely high mortality rates, as well as death and desertion by many of its guards. During the 14 months of its existence, Andersonville accounted for 43 percent of all Union deaths in Civil War prisons.