This is the last remaining wall of the infamous military prison in Alton, Ill. Originally shut down before the Civil War due to its poor condition, the prison was reopened to house prisoners of war. Thousands died within its walls, especially during an outbreak of yellow fever. At one point the city required all those dying within the prison to be buried in an island in the Mississippi River to avoid sickening the whole town.
The prison was closed after the war, and most of its stones were taken to form the foundations of houses throughout Alton. Only this one wall remains, moved from its original location, as a monument to the Alton prison.