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 October 4, 2026.
Union County, South Dakota, has about 17,000 residents (2024 Census Bureau estimate). A person kept in custody after an arrest in Union County is held at the county jail, run by the Union 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: Union County public records, Union County arrest records, Union County warrants, Union County criminal records, Union County court records, South Dakota arrest records and South Dakota inmate search.
Finding Someone in Custody in Union County
A person kept in custody after an arrest in Union County is held at the county jail, run by the Union County Sheriff's Office, whichever agency made the arrest.
SearchSystems opened and checked the jail page of the Union County Sheriff's Office at unioncountysd.gov/unioncountysdsheriff/inmates (page title: Inmates | Union County, South Dakota), which answered when SearchSystems opened it on September 24, 2026.
That page is the office's jail information page rather than a roster.
The Union County Jail by the Numbers
On an average day in 2019 the jail held about 35 people. Its rated capacity in 2019 was 40 beds, and it ran at 88 percent of it that year. The figures are from the Vera Institute of Justice's Incarceration Trends data.
Union County has about 17,000 residents (2024 Census Bureau estimate), so the jail holds about 20 people for every 10,000 residents.
Who Books People Into the Union County Jail
The Union County Sheriff's Office and the agencies that report for North Sioux City, Beresford, Elk Point and Jefferson make the arrests that end in a booking in Union County.
The largest arrest counts reported to the FBI were North Sioux City's 158 for 2025, Beresford's 73 for 2025 and the Union County Sheriff's Office's 71 for 2025.
Together, the four agencies in Union County with all twelve months of 2025 on file reported 323 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 Union 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 South Dakota Department of Corrections lists its inmates at doc.sd.gov/adult-corrections/offender-locator.
Frequently Asked Questions
How do I find an inmate in Union County?
Ask the Union County Sheriff's Office; its jail page SearchSystems verified is at unioncountysd.gov.
How many people are in the Union County jail?
About 35 on an average day in 2019, the latest year in the Vera Institute's jail data, against a rated capacity of 40 beds.
Where do people sentenced to prison in Union County go?
To a facility of the South Dakota Department of Corrections; its inmate locator is at doc.sd.gov/adult-corrections/offender-locator.
Is this the official Union 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.