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 September 25, 2026.
Janesville, Wisconsin, in Rock County, has about 66,000 residents (2024 Census Bureau estimate). A person kept in custody after an arrest in Janesville is held at the county jail, run by the Rock 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: Janesville public records, Rock County inmate search, Janesville arrest records, Janesville warrants, Janesville criminal records, Janesville court records, Wisconsin arrest records and Wisconsin inmate search.
Finding Someone in Custody in Janesville
A person kept in custody after an arrest in Janesville is held at the county jail, run by the Rock County Sheriff's Office, whichever agency made the arrest.
SearchSystems opened and checked the jail page of the Rock County Sheriff's Office at co.rock.wi.us/departments/sheriff-s-office/jail (page title: Jail | Rock County, WI), phone 608-757-8000, 200 East US Highway 14 Janesville, WI 53545, Monday - Friday 7:00 am - 3:00 pm, which answered when SearchSystems opened it on September 23, 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 608-757-8000.
The Rock County Jail by the Numbers
On an average day in 2025 the jail held about 360 people, down from about 440 in 2019. Its rated capacity in 2025 was 505 beds, and it ran at 71 percent of it that year. The figures are from the Vera Institute of Justice's Incarceration Trends data.
Rock County has about 165,000 residents (2024 Census Bureau estimate), so the jail holds about 22 people for every 10,000 residents.
Who Books People Into the Rock County Jail
The Rock County Sheriff's Office and the agency that reports for Janesville (filed by the FBI as Janesville Police Department) make the arrests that end in a booking in and around Janesville.
The Brodhead Police Department is listed by the FBI across two counties including Rock County, so its arrests are not broken out for Rock County here.
The largest arrest counts reported to the FBI were Janesville's 3,504 for 2025, Beloit's 2,623 for 2024 and the Rock County Sheriff's Office's 1,573 for 2025.
Together, the six agencies in Rock County with all twelve months of 2025 on file reported 5,739 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 Janesville arrest records.
From the Jail to State Prison
The jail holds people awaiting trial and people serving short sentences. A person sentenced to prison in Rock County serves the sentence in a facility of the Wisconsin Department of Corrections, whose inmate locator is at appsdoc.wi.gov/lop/welcome.
Frequently Asked Questions
How do I find an inmate in Janesville?
Ask the Rock County Sheriff's Office at 608-757-8000; its jail page SearchSystems verified is at co.rock.wi.us.
How many people are in the Rock County jail?
About 360 on an average day in 2025, the latest year in the Vera Institute's jail data, against a rated capacity of 505 beds.
What is the phone number for the Rock County jail?
608-757-8000, the number on the page of the Rock County Sheriff's Office SearchSystems verified.
Where do people sentenced to prison in Rock County go?
To a facility of the Wisconsin Department of Corrections; its inmate locator is at appsdoc.wi.gov/lop/welcome.
Is this the official Janesville 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.