The San Mateo County Inmate Population
San Mateo County jail custody is run by the San Mateo County Sheriff's Office Corrections Division. The local system is not a single building. It includes Maguire Correctional Facility, Maple Street Correctional Center, the Men's and Women's Transitional Facilities, and the Alternative Sentencing Bureau. San Francisco County Jail #3 is also physically in San Mateo County, but it is operated by the San Francisco Sheriff's Office and holds San Francisco jail inmates, not San Mateo County arrestees.
Maguire Correctional Facility is the main San Mateo County jail. The county's Maple Street opening materials state that all bookings occur at Maguire, and that maximum-security males remain there. Maple Street added modern housing, program space, and dedicated transitional housing. That matters for the San Mateo County inmate population because a person may be booked at Maguire, housed at Maple Street after classification, moved into transitional housing, or approved for an alternative program instead of full-time jail confinement.
The county jail roster is only the current-custody side of the population. A person sentenced to California state prison moves into CDCR CIRIS, not the San Mateo County roster. A sentenced federal prisoner is searched through the BOP inmate locator. Immigration custody is searched through ICE ODLS. Keeping those systems separate prevents the common mistake of treating a no-result in one locator as proof that the person was never arrested or is not held somewhere else.
San Mateo County Inmate Population Statistics
Published San Mateo County population figures require careful attribution because the captured sources do not provide one clean current rated-capacity table for every local facility. The sheriff's site footer and about materials list county residents and Sheriff's Office staffing. The county's 2016 Maple Street release gives design capacity and building size for Maple Street. Separate monitoring sources list bed counts for Maguire and Maple Street, but those are not the county's own current capacity table.
| Measure | Figure | Source context |
|---|---|---|
| County residents | 764,442 | Sheriff site footer, inspected May 31, 2026. |
| Sheriff's Office employees | 800 | Sheriff about material and footer context. |
| Calls for service | 103,089 in 2025 | Sheriff site footer statistic block. |
| Maple Street design capacity | 832 beds | County of San Mateo CEO ribbon-cutting release from 2016. |
| Maple Street building size | 260,000 square feet | County of San Mateo CEO release. |
| County Jail #3 capacity | 768 beds | SF.gov jail population page, July 2024 context. |
The most reliable way to track a current jail count is the BSCC Jail Profile Survey dashboard, which is the statewide source for county jail trends. The San Mateo research captured the dashboard page but not a verified county export. For that reason, the San Mateo County inmate population pages use the dashboard as the official trend source without inventing monthly averages that were not extracted from it.
San Mateo County Jail Population Trends
San Mateo County's jail-population history is tied to facility conditions as much as raw count. County materials say the Jail Planning Unit formed in 2007 because Maguire had significant overcrowding and the former women's jail had major maintenance problems, including flooding. Maple Street opened in 2016 as a three-story correctional center with housing, classrooms, and a commercial kitchen built for culinary training.
The newer population story focuses on short stays, health needs, and programs. A 2024 sheriff release said about 70 percent of people booked into Maguire had alcohol or drug addiction, around 48 percent had a form of mental illness, and two-thirds left within five days. Those figures explain why booking, screening, release planning, and court action can all affect the San Mateo County inmate population within a few days.
| Period | San Mateo County jail population context | Use on records pages |
|---|---|---|
| 2007 | Jail Planning Unit formed in response to overcrowding and old facility conditions. | Shows why Maguire and Maple Street roles differ. |
| 2016 | Maple Street opened with 832-bed design capacity and program space. | Use as design history, not a current live count. |
| 2024 | Sheriff release highlighted addiction, mental illness, and short stays among Maguire bookings. | Explains why locator status can change quickly. |
| 2025 | County and sheriff reported work with monitoring groups on mental-health policies and programs. | Use factual, dated language and avoid overstating court orders. |
| Current | BSCC Jail Profile Survey is the statewide dashboard for official jail trend data. | Use the dashboard rather than unsupported estimates. |
Who Makes Up San Mateo County Custody
The San Mateo County inmate population includes pretrial detainees, people serving county jail sentences, people in classification after booking, minimum-security inmates in transitional housing, and court-approved participants in alternatives such as work furlough or electronic monitoring. Penal Code section 4000 describes county jails as places kept by sheriffs for people charged and committed for trial, people confined under lawful process, witnesses, sentenced jail inmates, and certain supervision violators.
That statutory frame is broader than a roster search. A San Mateo County inmate record may start with an arrest by a city police department, sheriff patrol bureau, transit police assignment, or another local agency. The City of San Mateo's official inmate search page points users back to the county jail locator rather than a city roster, which reinforces the county role in booking and current custody.
- Booking
- Jail intake after arrest, including identification, property handling, screening, and creation of a custody record.
- Classification
- Jail review of housing, security, medical, mental-health, and program needs.
- Detainer
- A hold or request from another agency that can affect release even when local bail appears available.
- CDCR
- The California state prison system, separate from San Mateo County jail custody.
Laws Governing San Mateo County Inmates
California law explains why some jail facts are public while other records stay restricted. Basic arrest and booking facts can be releasable, but full investigative files, medical information, security details, and many criminal court documents are not all posted online. The San Mateo County inmate population should therefore be checked through official custody, court, and records channels instead of a single public database.
Government Code section 7923.610 requires release of specified arrest information such as name, booking dates, bail, current holding place, charges, and holds unless an exception applies.
Penal Code section 4000 describes who may be held in county jails kept by sheriffs.
Penal Code section 6030 gives BSCC authority to set minimum standards for local detention facilities.
BSCC Title 15 and Title 24 regulations govern state jail standards and local detention requirements.
Search the San Mateo County Inmate Population
The official current-custody search is the San Mateo County Sheriff's Office Inmate Locator. The portal says a person should enter both first and last name, then select Find Inmate. It also offers a middle-name field, a gender dropdown, and a phonetic-search checkbox for uncertain spelling. The portal warns that information can change as people move through the judicial process and that some names may not appear because of legal exemptions.
The official inmate locator screenshot captured for San Mateo County shows the public search fields used before a custody result is returned.
The screenshot is useful because it confirms that the public search screen is name based and does not expose a booking-number search field.
- Open the San Mateo County inmate locator.
- Enter the person's first and last name because the page says both are needed.
- Add a middle name when known, or leave it blank when uncertain.
- Use the gender dropdown only when it helps narrow common names.
- Check phonetic search if spelling may be wrong.
- Select Find Inmate, then verify any custody status before acting on it.
| Field | Type | Required | San Mateo note |
|---|---|---|---|
| Enter First Name | Text | Instruction says yes | Use with last name. |
| Enter Middle Name | Text | No | Useful for common names. |
| Enter Last Name | Text | Instruction says yes | Use with first name. |
| Gender | Dropdown | No | All, Male, or Female. |
| Use phonetic search | Checkbox | No | Use when spelling is uncertain. |
San Mateo County Inmate Record Fields
The sheriff's 2016 locator release says the search result can provide facility location, pending charges, custody status, next court date, and bail amount. A live sample profile was not captured in the research, so the San Mateo County inmate population pages do not promise booking photos, housing pod, release date, physical descriptors, or booking number on the public roster unless those fields are later verified.
| Record field | What it means |
|---|---|
| Facility location | The facility known to the sheriff, such as Maguire or Maple Street. |
| Pending charges | Booking or jail charges, not always the final filed court charges. |
| Custody status | Current jail status known to the sheriff at the time shown. |
| Next court date | Upcoming court appearance known to the jail system. |
| Bail amount | Amount known to the sheriff, subject to court changes and holds. |
For more detail on the current roster fields, the San Mateo County jail inmate records page separates jail records from court, CDCR, federal, and ICE lookup systems.
San Mateo County Jail Versus Prison Search
The San Mateo County inmate population changes systems after sentencing or transfer. County jail custody covers the local arrest and short-sentence stage. CDCR covers sentenced California prison custody. BOP covers sentenced federal prison custody. ICE ODLS covers immigration detention. VINELink can help with custody status notifications, but it is not a substitute for the official locator or court record.
| Situation | Official system | What it can answer |
|---|---|---|
| New San Mateo County arrest | San Mateo inmate locator or Maguire phone line | Current custody, facility, pending charge, court date, bail if shown. |
| Formal charges after arrest | San Mateo MIDX and court access | Case number, party, filing date, and court index details. |
| State prison sentence | CDCR CIRIS | State prison location and state custody status. |
| Federal prison sentence | BOP locator | Federal register number, location, and release status. |
| Immigration detention | ICE ODLS | ICE custody location/status, not local criminal charges. |
San Mateo County Detention Facilities
The facility map for San Mateo County includes four San Mateo Sheriff Corrections locations and one San Francisco jail located inside the county. The distinction is important. San Francisco County Jail #3 is a San Bruno building, but it is not searched through the San Mateo inmate locator.
- Maguire Correctional Facility - main county jail, booking, male custody, and maximum-security male housing.
- Maple Street Correctional Center - county correctional center with male, female, transitional, and program housing.
- Men's and Women's Transitional Facilities - minimum-security work-oriented housing at the Maple Street campus.
- Alternative Sentencing Bureau - program office for work program, electronic monitoring, and work furlough.
- San Francisco County Jail #3 - San Francisco Sheriff's Office jail in San Bruno, separate from San Mateo custody.
San Mateo County Inmate Population FAQ
How do I search the San Mateo County inmate population? Use the San Mateo County Sheriff's Office Inmate Locator for current county custody. Enter first and last name, then use the phone fallback or records process if a name does not appear.
Does a missing name mean the person is not in jail? No. The county locator itself warns that some names may not appear because of disclosure exemptions, and new court or custody events can change the record.
Where are sentenced San Mateo County inmates searched? Sentenced California prisoners are searched through CDCR CIRIS after transfer. County jail records do not follow a person into state prison.
Are mugshots guaranteed on the roster? No official San Mateo source in the research confirmed public booking photos on the current locator. The San Mateo County jail mugshots page explains the request path.
Who runs the San Mateo County jail system? The San Mateo County Sheriff's Office Corrections Division runs Maguire, Maple Street, transitional housing, and alternative sentencing programs.
Is San Francisco County Jail #3 a San Mateo jail? No. It is physically in San Bruno, but it is operated by San Francisco and holds San Francisco jail inmates.
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