Reviewed and updated October 9, 2026 by the SearchSystems.net editorial team. The arrest counts are the ones the agency reported to the FBI, through 2025. 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.
O'Fallon, Illinois, in St. Clair County, has about 32,000 residents (2024 Census Bureau estimate), and its arrests are reported to the FBI by an agency of its own. An arrest in the city leaves the same records whoever makes it: the arresting agency's report, the record of anyone held at the county jail, and, if the State's Attorney files charges, a case in the Circuit Court of St. Clair County. This guide says who keeps each one, what it costs and who may see it, with the arrest counts the agency reported.
This guide covers who makes arrests, how many arrests, booking and the jail, finding an arrest, copies and common questions.
Related guides: O'Fallon public records, St. Clair County arrest records, Illinois arrest records and Illinois inmate search.
Who Makes Arrests in O'Fallon
The FBI lists O'Fallon with an arrest reporting agency of its own, filed as O'Fallon Police Department. It reported 744 arrests for 2025. A city is listed separately whether the officers are the city's own or the sheriff's under contract; the FBI's list does not say which.
Outside the city, the St. Clair County Sheriff's Office is the county agency. It reported 248 arrests for 2025.
The FBI's agency list also places these agencies in St. Clair County: Alton and Southern Railway and Union Pacific Railroad in St. Clair County (other); Southwestern Illinois College (campus police).
How Many Arrests O'Fallon Reports
The FBI publishes every agency's monthly arrest counts on the Crime Data Explorer. These are the full-year totals, all offenses, as the FBI held them on October 8, 2026; a year with months missing or not reported is left out.
- O'Fallon: 744 for 2025, 669 for 2024, 863 for 2023, 728 for 2022 and 471 for 2021.
O'Fallon's 744 arrests in 2025 were up 11 percent from 669 in 2024.
Through August 2026, O'Fallon reported 479 arrests, against 500 in the same months of 2025.
Across St. Clair County, the 17 agencies with all twelve months of 2025 on file reported 6,114 arrests between them.
Booking: Where People Arrested in O'Fallon Are Held
The county jail is where a person arrested in O'Fallon and kept in custody ends up, whichever agency made the arrest, though a city department may hold someone in its own cells first and a person cited and released at the scene is never booked. The jail's record of each person held, with the charges, is a public record of the arrest, and once the person is released or sentenced the record continues in the court file.
On an average day in 2021 the jail held about 450 people, up from about 350 in 2019. Its rated capacity in 2019, the last year with a capacity figure, was 418 beds, and it ran at 84 percent of it that year. The figures are from the Vera Institute of Justice's Incarceration Trends data.
SearchSystems opened and checked the jail page of the St. Clair County Sheriff's Office at co.st-clair.il.us/departments/sheriffs-department (page title: Sheriff's Department | Departments | St. Clair), phone (618) 277-3505, which answered when SearchSystems opened it on October 4, 2026.
A sentence of more than a year is served in state prison; the Illinois Department of Corrections lists its inmates at idoc.illinois.gov/offender/inmatesearch.html.
How to Find Out About an Arrest in O'Fallon
For O'Fallon the place to look is the State's Attorney, which decides whether an arrest becomes a charge (its page is at co.st-clair.il.us/departments/states-attorney, phone (618) 277-3892).
Illinois is one of the states that lets anyone look up another person's statewide criminal history: conviction information is public under the Uniform Conviction Information Act, through the Illinois State Police. That record shows what agencies reported to the state, which is wider than one county's court index but can lag it.
Getting a Copy of an Arrest Record in O'Fallon
An arrest report belongs to the agency whose officer wrote it, and that agency releases it, not the court or the jail. Under the Illinois Freedom of Information Act the agency must answer within 5 business days, with one 5-day extension, and it may charge copying only after the first 50 pages.
- An arrest by the agency that reports for O'Fallon: its own records unit.
- An arrest by the St. Clair County Sheriff's Office: ask its records unit, reached through the office at (618) 277-3505.
- A defendant who has been charged gets the report through the case: the State's Attorney, (618) 277-3892, handles discovery for pending cases.
- Any county record that is not posted: the county records request page SearchSystems verified is at stclaircountyil.justfoia.com (page title: St. Clair County, IL Public Portal | JustFOIA).
- Your own statewide record: a name-based or fingerprint-based request to the Illinois State Police.
The St. Clair County guide covers every agency in the county: St. Clair County arrest records.
Frequently Asked Questions
How many arrests are made in O'Fallon each year?
O'Fallon reported 744 arrests to the FBI for 2025, its latest full year.
How do I find out if someone is in jail in O'Fallon?
Ask the St. Clair County Sheriff's Office at (618) 277-3505; its jail page SearchSystems verified is at co.st-clair.il.us.
Where are people arrested in O'Fallon booked?
Those kept in custody go to the county jail, run by the St. Clair County Sheriff's Office; a person cited and released at the scene is not booked.
Are arrest records public in O'Fallon?
The court files of criminal cases are public, and so is the statewide criminal history kept by the Illinois State Police: conviction information is public under the Uniform Conviction Information Act. The arrest report itself is released by the agency that made the arrest, under the Illinois Freedom of Information Act.
How do I get a copy of an arrest report in O'Fallon?
From the agency that made the arrest: the agency that reports for O'Fallon for its own arrests, the St. Clair County Sheriff's Office for the sheriff's. Under the Illinois Freedom of Information Act the answer is due within 5 business days, with one 5-day extension; the county records request page SearchSystems verified is at stclaircountyil.justfoia.com.
Is this the official O'Fallon website?
No. SearchSystems.net is an independent public records guide, online since 1997. It links to the official city, county, court and state offices described above and does not hold records, charge for them or take requests.