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 October 9, 2026.
Arnold, Missouri, in Jefferson County, has about 21,000 residents (2024 Census Bureau estimate). A person kept in custody after an arrest in Arnold is held at the county jail, run by the Jefferson 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: Arnold public records, Jefferson County inmate search, Arnold arrest records, Arnold warrants, Arnold criminal records, Arnold court records, Missouri arrest records and Missouri inmate search.
Finding Someone in Custody in Arnold
A person kept in custody after an arrest in Arnold is held at the county jail, run by the Jefferson County Sheriff's Office, whichever agency made the arrest.
SearchSystems opened and checked the jail page of the Jefferson County Sheriff's Office at jeffcomo.gov/m/directory/department?did=50 (page title: Staff Directory, Sheriff), phone 636-797-5000, 400 First Street Justice Center Hillsboro, MO 63050, which answered when SearchSystems opened it on October 9, 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 636-797-5000.
The Jefferson County Jail by the Numbers
On an average day in 2019 the jail held about 320 people. Its rated capacity in 2019 was 371 beds, and it ran at 86 percent of it that year. The figures are from the Vera Institute of Justice's Incarceration Trends data.
Jefferson County has about 232,000 residents (2024 Census Bureau estimate), so the jail holds about 14 people for every 10,000 residents.
Who Books People Into the Jefferson County Jail
The Jefferson County Sheriff's Office and the agency that reports for Arnold (filed by the FBI as Arnold Police Department) make the arrests that end in a booking in and around Arnold.
The FBI's agency list also places these agencies in Jefferson County: Jefferson College (campus police); the Dunklin R-5 School District (other agency).
The Eureka Police Department is listed by the FBI across two counties including Jefferson County, so its arrests are not broken out for Jefferson County here.
The largest arrest counts reported to the FBI were the Jefferson County Sheriff's Office's 1,731 for 2025, Arnold's 454 for 2023 and De Soto's 400 for 2025.
Together, the six agencies in Jefferson County with all twelve months of 2025 on file reported 2,576 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 Arnold 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 Jefferson County serves the sentence in a facility of the Missouri Department of Corrections, whose inmate locator is at web.mo.gov/doc/offSearchWeb.
Frequently Asked Questions
How do I find an inmate in Arnold?
Ask the Jefferson County Sheriff's Office at 636-797-5000; its jail page SearchSystems verified is at jeffcomo.gov/m/directory/department?did=50.
How many people are in the Jefferson County jail?
About 320 on an average day in 2019, the latest year in the Vera Institute's jail data, against a rated capacity of 371 beds.
What is the phone number for the Jefferson County jail?
636-797-5000, the number on the page of the Jefferson County Sheriff's Office SearchSystems verified.
Where do people sentenced to prison in Jefferson County go?
To a facility of the Missouri Department of Corrections; its inmate locator is at web.mo.gov/doc/offSearchWeb.
Is this the official Arnold 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.