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 2, 2026.
Marengo, Illinois, in McHenry County, has about 7,700 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 McHenry 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: Marengo public records, McHenry County arrest records, Illinois arrest records and Illinois inmate search.
Who Makes Arrests in Marengo
The FBI lists Marengo with an arrest reporting agency of its own, filed as Marengo Police Department. It reported 158 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 McHenry County Sheriff's Office is the county agency. It reported 820 arrests for 2025.
The FBI's agency list also places these agencies in McHenry County: McHenry County College (campus police); the McHenry County Conservation District and the Crystal Lake Park District (other).
How Many Arrests Marengo Reports
Each agency reports its arrests to the FBI by month, and the FBI publishes them 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.
- Marengo: 158 for 2025, 162 for 2024 and 111 for 2023.
Marengo's 158 arrests in 2025 were down 2.5 percent from 162 in 2024.
Across McHenry County, the 21 agencies with all twelve months of 2025 on file reported 4,544 arrests between them.
Booking: Where People Arrested in Marengo Are Held
A person kept in custody after an arrest in Marengo is held at the county jail, whichever agency made the arrest, apart from the short stay some city departments' own holding cells allow; a person cited and released at the scene is not booked at all. The jail's record of each person held, with the charges, is a public record of the arrest, and the court file takes over from there.
On an average day in 2024 the jail held about 380 people, down from about 460 in 2019. Its rated capacity in 2023, the last year with a capacity figure, was 650 beds, and it ran at 29 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 McHenry County Sheriff's Office at mchenrysheriff.org (page title: McHenry County IL Sheriff's Office), which answered when SearchSystems opened it on September 23, 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 Marengo
For Marengo the place to look is the State's Attorney, which decides whether an arrest becomes a charge (its page is at mchenrycountyil.gov/departments/state-s-attorney-s-office, phone (815) 334-4159).
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 Marengo
The report of an arrest is released by the agency that made it; the jail and the court hold their own records of the same event, but not the report. 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 Marengo police: the police records page SearchSystems verified at cityofmarengo.com/request-public-records (page title: REQUEST PUBLIC RECORDS), phone 815.568.7112, 132 E. Prairie Street Marengo, IL 60152, which answered when SearchSystems opened it on September 26, 2026.
- An arrest by the McHenry County Sheriff's Office: ask its records unit.
- A defendant who has been charged gets the report through the case: the State's Attorney, (815) 334-4159, handles discovery for pending cases.
- Your own statewide record: a name-based or fingerprint-based request to the Illinois State Police.
The McHenry County guide covers every agency in the county: McHenry County arrest records.
Frequently Asked Questions
How many arrests are made in Marengo each year?
Marengo reported 158 arrests to the FBI for 2025, its latest full year.
How do I find out if someone is in jail in Marengo?
Ask the McHenry County Sheriff's Office; its jail page SearchSystems verified is at mchenrysheriff.org.
Where are people arrested in Marengo booked?
Those kept in custody go to the county jail, run by the McHenry County Sheriff's Office; a person cited and released at the scene is not booked.
Are arrest records public in Marengo?
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 Marengo?
From the agency that made the arrest: the Marengo police for its own arrests, the McHenry 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.
Is this the official Marengo 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.