Reviewed and updated October 9, 2026 by the SearchSystems.net editorial team. The arrest counts are the ones each agency reported to the FBI, as the FBI held them on October 8, 2026. The jail figures are from the Vera Institute of Justice's Incarceration Trends data. Every office link was opened and checked against the office's own site between September 23, 2026 and October 9, 2026.
Jefferson County, Illinois, has about 36,000 residents (2024 Census Bureau estimate). A person kept in custody after an arrest in Jefferson County is held at the county jail, run by the Jefferson County Sheriff's Office, and the jail's record of each person held is a public record. This guide says where to look for someone in custody, what the jail holds and who books people into it.
This guide covers the search, the jail, who books people, state prison and common questions.
Related guides: Jefferson County public records, Jefferson County arrest records, Jefferson County warrants, Jefferson County criminal records, Jefferson County court records, Illinois arrest records and Illinois inmate search.
Finding Someone in Custody in Jefferson County
The county jail, run by the Jefferson County Sheriff's Office, holds everyone kept in custody after an arrest in Jefferson County, from every agency.
SearchSystems opened and checked the jail page of the Jefferson County Sheriff's Office at ilsheriff.org/county/jefferson (page title: Jefferson County | Illinois Sheriffs' Association), phone (217) 753-2372, 911 Casey Ave., Mt. Vernon, IL 62864, a site that blocks automated checks (HTTP 403), so open it in a browser.
That page is the office's jail information page rather than a roster, so a search for a particular person goes through the office at (217) 753-2372.
The Jefferson County Jail by the Numbers
On an average day in 2023 the jail held about 170 people, down from about 180 in 2019. Its rated capacity in 2023 was 252 beds, and it ran at 67 percent of it that year. The figures are from the Vera Institute of Justice's Incarceration Trends data.
Jefferson County has about 36,000 residents (2024 Census Bureau estimate), so the jail holds about 47 people for every 10,000 residents.
Who Books People Into the Jefferson County Jail
The Jefferson County Sheriff's Office and the agencies that report for Mount Vernon and Ina make the arrests that end in a booking in Jefferson County.
The FBI's agency list also places one more agency in Jefferson County: Rend Lake College (campus police).
The largest arrest counts reported to the FBI were Mount Vernon's 203 for 2025, the Jefferson County Sheriff's Office's 11 for 2025 and Ina's 2 for 2025.
Together, the three agencies in Jefferson County with all twelve months of 2025 on file reported 216 arrests to the FBI that year. Those kept in custody were booked into the county jail; a person cited and released at the scene was not.
The counts, agency by agency and year by year, are in Jefferson County arrest records.
From the Jail to State Prison
A sentence of more than a year is served in state prison, not the jail; the Illinois Department of Corrections lists its inmates at idoc.illinois.gov/offender/inmatesearch.html.
Frequently Asked Questions
How do I find an inmate in Jefferson County?
Ask the Jefferson County Sheriff's Office at (217) 753-2372; its jail page SearchSystems verified is at ilsheriff.org/county/jefferson.
How many people are in the Jefferson County jail?
About 170 on an average day in 2023, the latest year in the Vera Institute's jail data, against a rated capacity of 252 beds.
What is the phone number for the Jefferson County jail?
(217) 753-2372, the number on the page of the Jefferson County Sheriff's Office SearchSystems verified.
Where do people sentenced to prison in Jefferson County go?
To a facility of the Illinois Department of Corrections; its inmate locator is at idoc.illinois.gov/offender/inmatesearch.html.
Is this the official Jefferson County website?
No. SearchSystems.net is an independent public records guide, online since 1997. It links to the official county, court and state offices described above and does not hold records, charge for them or take requests.