Alton Military Prison

Alton Military Prison is the ruins of a former penitentiary in Illinois that served as a military detention facility during the American Civil War. The remaining stone walls show the layout of the original complex that once held thousands of prisoners.

The facility was founded in 1833 as Illinois' first state penitentiary to hold convicted criminals. In 1862, it was converted into a military prison to house Confederate soldiers and civilians during the Civil War.

The site tells the story of the prisoners held here and preserves their experiences through local records and exhibitions. Visitors can connect with this important chapter in regional history today.

The remaining wall section is now part of the Christian Hill Historic District and protected as a historic site. Visitors can walk around the ruins on foot, though the grounds are uneven and parking is limited nearby.

During a smallpox outbreak in the prison, authorities set up a quarantine hospital on an island in the Mississippi River. That island has since become submerged beneath the river's waters.

Location: Alton

GPS coordinates: 38.89170,-90.19060

Latest update: December 9, 2025 18:48