Andersonville Prison was a confederate prison-of-war camp located in Georgia from February 1864 to the end of the war in April 1865. There were up to 33,000 union soldiers in the camp at one time. The camp was designed to hold only 6,000 to 10,000 prisoners. The death rate was horrendous with up to 130 soldiers dying per day. Nearly 13,000 soldiers died mainly from disease and starvation. In fact 29% of the prisoners died during the 14 months the camp existed.
The site is now called the Andersonville National Historic site dedicated to all American prisoners of war. There are soldiers of many other wars buried there including WWI , WW2, Vietnam, Korean and the Mexican American War. The graves now total ~20,000.