The state closed Sheridan 17 months ago because of budget cutbacks.
Governor Rod Blagojevich says the 1,300-bed facility will be now the largest state-run drug prison and community crime reduction program in the country.
Sheridan will provide drug treatment and vocational classes to offenders who are projected to serve six to 24 months in prison. Upon their release, they will participate in a closely monitored community re-entry and supervision program.
The medium-security facility was built in 1941 and is located 25 miles southwest of Aurora. More than 400 jobs will be restored when it reopens.