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 30, 2026.
Mason County, Washington, has about 70,000 residents (2024 Census Bureau estimate). A person kept in custody after an arrest in Mason County is held at the county jail, run by the Mason 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: Mason County public records, Mason County arrest records, Mason County warrants, Mason County criminal records, Mason County court records, Washington arrest records and Washington inmate search.
Finding Someone in Custody in Mason County
The county jail, run by the Mason County Sheriff's Office, holds everyone kept in custody after an arrest in Mason County, from every agency.
SearchSystems opened and checked the jail page of the Mason County Sheriff's Office at masoncountywa.gov/departments/sheriff/index.php (page title: Mason County WA Government), phone 360-427-9670, 322 North 3rd Street, Shelton, WA 98584, 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 360-427-9670.
The Mason County Jail by the Numbers
On an average day in 2021 the jail held about 87 people, down from about 120 in 2018. The figures are from the Vera Institute of Justice's Incarceration Trends data.
Mason County has about 70,000 residents (2024 Census Bureau estimate), so the jail holds about 12 people for every 10,000 residents.
Who Books People Into the Mason County Jail
The Mason County Sheriff's Office and the agency that reports for Shelton make the arrests that end in a booking in Mason County.
The largest arrest counts reported to the FBI were the Mason County Sheriff's Office's 643 for 2025 and Shelton's 481 for 2025.
Together, the two agencies in Mason County with all twelve months of 2025 on file reported 1,124 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 Mason County 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 Mason County serves the sentence in a facility of the Washington State Department of Corrections, whose inmate locator is at doc.wa.gov/records/incarcerated-data-search/incarcerated-search.
Frequently Asked Questions
How do I find an inmate in Mason County?
Ask the Mason County Sheriff's Office at 360-427-9670; its jail page SearchSystems verified is at masoncountywa.gov.
How many people are in the Mason County jail?
About 87 on an average day in 2021, the latest year in the Vera Institute's jail data.
What is the phone number for the Mason County jail?
360-427-9670, the number on the page of the Mason County Sheriff's Office SearchSystems verified.
Where do people sentenced to prison in Mason County go?
To a facility of the Washington State Department of Corrections; its inmate locator is at doc.wa.gov.
Is this the official Mason 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.