From the Illinois State Archives:
This database provides an index for the Registers of Prisoners received at the Illinois State Penitentiary at Alton Prison (1833-1841; 1847-1858), the Illinois State Penitentiary at Joliet (ca. 1858-1901) and Southern Illinois penitentiary at Chester (Menard) (ca. 1865-1908). A complete history of Illinois prisons is accessible here (http://archon.ilsos.net/?p=creators/creator&id=36). Registers provide information about the prisoner, including personal history and family history.
Digitization of this collection was developed pursuant to a grant awarded by the Illinois State Library, a Department of the Office of Secretary of State using state grant funds.
For more information, see Department of Corrections - RG 243 | Illinois State Archives.