While the Alton Military Prison operated during the Civil War, approximately 1,570 soldiers and civilians held there died, along with about 200 Union soldiers who served as guards. Burials took place in three locations: the old penitentiary burial ground, Alton Cemetery, and Smallpox Island. Confederate soldiers, prisoners classified as guerillas, and civilian prisoners who died at the prison were buried in a plot set aside by the State of Illinois for inmates who died at the Illinois State Penitentiary; thirty burials had taken place there before the penitentiary closed in 1858. Prisoners were buried in trenches, sometimes two to a casket, with graves marked by numbered wooden stakes. After the war the cemetery was largely forgotten and was used for a time as a cow pasture. In 1897, the United States Congress funded the marking of graves of Confederate soldiers who died in Northern prisons, but the original stakes had disappeared and no record of individual grave locations remained. Through the urging of the local Sam Davis Chapter of the Daughters of the Confederacy, a monument was erected listing the names of 1,354 Confederate soldiers, although some of those burials were on Smallpox Island. No provision was made to mark the graves of civilians who died in Union prisons, so their final resting place bears no mention of them. Union soldiers who died during service in Alton were buried in marked graves in the part of Alton Cemetery called Citizens Ground, including garrison troops guarding prisoners, Union soldiers held prisoner for various offenses, and a small number of soldiers who died while traveling through Alton on their way to war. In 1867, Congress passed the National Cemeteries Act and provided for proper burial of Union soldiers who died while in service. Their bodies were buried in what is now Alton National Cemetery, which contains 512 burials, including 204 from the Civil War era and at least two members of the U.S. Colored Infantry. In August 1863, a smallpox quarantine hospital opened on an island near the Missouri shore, where prisoners who developed smallpox were taken and remained until they recovered or died; those who died there were buried in a small cemetery on the island. The hospital was abandoned in March 1865 after high water flooded the island. After the war, that cemetery too was largely forgotten until construction of Lock & Dam 26 unearthed it in 1935; the graves were covered over and forgotten again until a new lock and dam threatened to expose the remains once more. The U.S. Army Corps of Engineers later commissioned research to locate the island cemetery, and the Smallpox Island Monument was dedicated in April 2002 with the names of 256 men and one woman believed to be buried near that spot.
