Once someone is found guilty of a crime and sentenced to more to more than a year in jail, that person is transferred to one of the states' 66 facilities. These prisons are part to the Illinois Department of Corrections.
The Illinois Department of Corrections (IDOC) allows you to search by last name, birth date, or inmate number to locate information regarding the status of a single inmate; this data is reported below.
It is unclear to what extent IDOC is amenable to a FOI request. The Chicago Justice Project has filed a minimal request with them to see what kinds of data fields they collect, but they have not responded.
There is likely some prison data that would be unavailable, even from a FOIA request. The unavailable jail data might serve as a good reference point for understanding what kinds of fields are not accessible from a correctional institution.
The "Open Data" below is available through single inmate search on the IDOC website. There is no bulk data made available. It is unclear what more data is collected.
It's also unclear what data is available through Illinois' Freedom of Information Act. Requesting more data from the Illinois Department of Corrections is still possible, though, by filing a request for data under Illinois' Freedom of Information Act (FOIA). You will need to send an email including: (1) your name and contact information, along with (2) a description of the records you are requesting. Please try to be reasonably specific for the data you are looking for so that they can more easily process your request.
The state of Oregon makes a very large amount of data about their prison available through their data portal. This includes forecasts of prison populations, census of current prison populations by institutions, and admissions data. The amount and quality of the data definitely makes Oregon the national standard for transparency in correctional data.
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