The prison building in Alton, Illinois, was constructed in 1833 to serve as the Illinois State Prison. Located in a low area close to the Mississippi River, the State of Illinois abandoned the prison in 1860 at the urging of social reformer Dorthea Dix, who complained about the unhealthy conditions there.
Soon after the outbreak of the Civil War, the federal government re-opened the facility as a Confederate prison. The maximum capacity of Alton prison was estimated at 800; in the last year of the war it held close to 1,900 Confederate prisoners.
As in many Confederate prisons, the inmate population was ravaged by disease, and over the course of the war smallpox claimed the lives of hundreds of prisoners. In an attempt to minimize the number of smallpox deaths, prison officials quarantined those stricken with the disease in a hospital on Tow Head Island, in the Mississippi River. Prisoners who died of smallpox were buried on the island itself. In the years after the Civil War, frequent flooding of the river eroded all of the grave markers. Today, the location of the smallpox hospital and the burials is unknown. Confederates who died from causes other than smallpox were interred two miles north of Alton, in an area known as “Buck Inn.” This became the official prison burial ground, and today is the location of the North Alton Confederate Cemetery.
(Source: North Alton Confederate Cemetery website)