During the early stages of the American Civil War the federal government refused to negotiate the exchange of prisoners as it did not recognize the Confederacy as a nation. In July, 1862, General John Dix of the Union Army and General D. H. Hill met and agreed an exchange. They decided that the rate of exchange was one general for every 60 enlisted men, a colonel for 15, a lieutenant for 4 and a sergeant for 2.

In 1863 General Henry Halleck became the Union representative involved in the exchange of prisoners. Under pressure from Edwin Stanton, the Secretary of War, these exchanges became less frequent. When Ulysses S. Grant became overall commander of the Union Army he brought an end to exchanges. General Benjamin F. Butler later said what Grant had told him: "He (Grant) said that I would agree with him that by the exchange of prisoners we get no men fit to go into our army, and every soldier we gave the Confederates went immediately into theirs, so that the exchange was virtually so much aid to them and none to us."

The decision of Ulysses S. Grant resulted in a rapid increase in the number of prisoners and so it was decided to build Andersonville Prison in Georgia. It was to be the Confederate's largest prison for captured soldiers. In April, 1864, General John Henry Winder, who was now in charge of all Union Army prisoners east of the Mississippi, appointed Henry Wirz as commandant of this new prison camp.

By August, 1864, there were 32,000 Union Army prisoners in Andersonville. The Confederate authorities did not provide enough food for the prison and men began to die of starvation. The water became polluted and disease was a constant problem. Of the 49,485 prisoners who entered the camp, nearly 13,000 died from disease and malnutrition.

When the Union Army arrived in Andersonville in May, 1865, photographs of the prisoners were taken and the following month they appeared in Harper's Weekly. The photographs caused considerable anger and calls were made for the people responsible to be punished for these crimes. It was eventually decided to charge General Robert Lee, James Seddon, the Secretary of War, and several other Confederate generals and politicians with "conspiring to injure the health and destroy the lives of United States soldiers held as prisoners by the Confederate States".

In August, 1865 President Andrew Johnson ordered that the charges against the Confederate generals and politicians should be dropped. However, he did give his approval for Henry Wirz to be charged with "wanton cruelty". Wirz appeared before a military commission headed by Major General Lew Wallace on 21st August, 1865. During the trial a letter from Wirz was presented that showed that he had complained to his superiors about the shortage of food being provided for the prisoners. However, former inmates at Andersonville testified that Wirz inspected the prison every day and often warned that if any man escaped he would "starve every damn Yankee for it." When Wirz fell ill during the trial Wallace forced to attend and was brought into court on a stretcher.

Henry Wirz was found guilty on 6th November and sentenced to death. He was taken to Washington to be executed in the same yard where those involved in the assassination of Abraham Lincoln had died. Alexander Gardner, the famous photographer, was invited to record the event.

The execution took place on the 10th November. The gallows were surrounded by Union Army soldiers who throughout the procedure chanted "Wirz, remember, Andersonville." Accompanied by a Catholic priest, Wirz refused to make a last minute confession, claiming he was not guilty of committing any crime.

Major Russell read the death warrant and then told Henry Wirz he "deplored this duty."Wirz replied that: "I know what orders are, Major. And I am being hanged for obeying them."

After a black hood was placed over his head, and the noose adjusted, a spring was touched and the trap door opened. However, the drop failed to break his neck and it took him two minutes to die. During this time the soldiers continued to chant: "Wirz, remember, Andersonville."