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 4, 2026.
Warren County, Illinois, has about 16,000 residents (2024 Census Bureau estimate). A person kept in custody after an arrest in Warren County is held at the county jail, run by the Warren 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: Warren County public records, Warren County arrest records, Warren County warrants, Warren County criminal records, Warren County court records, Illinois arrest records and Illinois inmate search.
Finding Someone in Custody in Warren County
The county jail, run by the Warren County Sheriff's Office, holds everyone kept in custody after an arrest in Warren County, from every agency.
SearchSystems opened and checked the jail page of the Warren County Sheriff's Office at warrencountyil.gov/offices/sheriff (page title: Warren County Sheriff's Office | Warren County IL), phone (309)734-8383, 121 North A Street Monmouth, IL 61462, which answered when SearchSystems opened it on October 4, 2026.
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 (309)734-8383.
The Warren County Jail by the Numbers
On an average day in 2023 the jail held about 6 people, down from about 26 in 2019. Its rated capacity in 2019, the last year with a capacity figure, was 42 beds, and it ran at 62 percent of it that year. The figures are from the Vera Institute of Justice's Incarceration Trends data.
Warren County has about 16,000 residents (2024 Census Bureau estimate), so the jail holds about 4 people for every 10,000 residents.
Who Books People Into the Warren County Jail
The Warren County Sheriff's Office and the agencies that report for Monmouth and Alexis make the arrests that end in a booking in Warren County.
The Avon Police Department is listed by the FBI across two counties including Warren County, so its arrests are not broken out for Warren County here.
The largest arrest counts reported to the FBI were Monmouth's 181 for 2025, the Warren County Sheriff's Office's 40 for 2025 and Alexis's 0 for 2020.
Together, the two agencies in Warren County with all twelve months of 2025 on file reported 221 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 Warren 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 Warren County?
Ask the Warren County Sheriff's Office at (309)734-8383; its jail page SearchSystems verified is at warrencountyil.gov/offices/sheriff.
How many people are in the Warren County jail?
About 6 on an average day in 2023, the latest year in the Vera Institute's jail data, against a rated capacity of 42 beds.
What is the phone number for the Warren County jail?
(309)734-8383, the number on the page of the Warren County Sheriff's Office SearchSystems verified.
Where do people sentenced to prison in Warren 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 Warren 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.