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 24, 2026 and September 30, 2026.
Petroleum County, Montana, has 525 residents (2024 Census Bureau estimate). A person kept in custody after an arrest in Petroleum County is held at the county jail, run by the Petroleum 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: Petroleum County public records, Petroleum County arrest records, Petroleum County warrants, Petroleum County criminal records, Petroleum County court records, Montana arrest records and Montana inmate search.
Finding Someone in Custody in Petroleum County
A person kept in custody after an arrest in Petroleum County is held at the county jail, run by the Petroleum County Sheriff's Office, whichever agency made the arrest.
SearchSystems opened and checked the jail page of the Petroleum County Sheriff's Office at petroleumcountymt.org/departments/sheriffs-department (page title: Sheriff’s Department | Petroleum County Montana), phone (406) 429-6551, 302 East Main, Winnett, MT 59087, which answered when SearchSystems opened it on September 30, 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 (406) 429-6551.
The Petroleum County Jail by the Numbers
On an average day in 2019 the jail held about 1 people. Its rated capacity in 2019 was 1 beds, and it ran at 38 percent of it that year. The figures are from the Vera Institute of Justice's Incarceration Trends data.
Petroleum County has 525 residents (2024 Census Bureau estimate), so the jail holds about 10 people for every 10,000 residents.
Who Books People Into the Petroleum County Jail
The Petroleum County Sheriff's Office makes the arrests that end in a booking in Petroleum County.
The Petroleum County Sheriff's Office reported 1 arrests to the FBI for 2025. 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 Petroleum 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 Montana Department of Corrections lists its inmates at offendersearch.mt.gov/conweb.
Frequently Asked Questions
How do I find an inmate in Petroleum County?
Ask the Petroleum County Sheriff's Office at (406) 429-6551; its jail page SearchSystems verified is at petroleumcountymt.org.
How many people are in the Petroleum County jail?
About 1 on an average day in 2019, the latest year in the Vera Institute's jail data, against a rated capacity of 1 beds.
What is the phone number for the Petroleum County jail?
(406) 429-6551, the number on the page of the Petroleum County Sheriff's Office SearchSystems verified.
Where do people sentenced to prison in Petroleum County go?
To a facility of the Montana Department of Corrections; its inmate locator is at offendersearch.mt.gov/conweb.
Is this the official Petroleum 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.