In just three years, more than 11,700 Confederate prisoners passed through the gates of the Alton Prison and were held captive with its walls. The Alton Prison, opened in 1833 and closed in 1860, was the first Illinois State Penitentiary. In December of 1861, after inspecting the facilities, Major General Henry Halleck, Commander of the Department of the Missouri, prepared to have the prison re-opened as a the Alton Federal Military Prison.
On Feb. 9, 1862, the first prisoners arrived at the prison. Inmates of the prison included Confederate soldiers, citizens imprisoned for treason acts, and bushwackers or guerillas imprisoned for acts against the government. Much of the time, the prison was overcrowded, prisoners were malnourished and had inadequate clothing.
Under these dilapidated conditions, prisoners were exposed to influenza, dysentery and small pox. The small pox epidemic grew in numbers, and the official military death toll listed 1,354 deceased. A monument dedicated to those who perished can be found at their burial site in the Confederate Cemetery.
After the war, the prison was privately purchased and building blocks were removed. The remaining small portion of the wall was restored in 1973 and may be visited today.