Contra Costa County, California
Contra Costa County · Martinez is the seat · Sacramento is the capital of California · Concord is a city · Richmond is a city · Walnut Creek is a city · Antioch is a city · Alameda is a different county
Martinez is the seat. Sacramento is the capital. Richmond, Concord, Walnut Creek, and Antioch are cities, not the hall.
Contra Costa County, California, was created 1850 as one of the original twenty-seven counties, and named contra costa — opposite coast from San Francisco, not Concord as the whole county. Martinez is the county seat. Sacramento is the capital of California. Martinez is not the capital. Concord is not the seat. Richmond is not the seat. Walnut Creek is not the seat. Antioch is not the seat — it is often the largest city, still not the hall. Do not read this page as Autauga-with-a-strait. Do not read this page as Alameda-with-a-refinery. Prattville is Autauga. Oakland is Alameda. Neither is this oval.
Concord is a city — not the hall. Richmond is a city — not the hall. Walnut Creek is a city — not the hall. Antioch is a city — not the hall. Pittsburg, Brentwood, San Ramon, Danville, Pleasant Hill, San Pablo, Hercules, Pinole, Martinez the city, and the other municipalities are cities — not the county government. Bay Point, Rodeo, Crockett, El Sobrante, Pacheco, Alamo, Blackhawk, Discovery Bay, Byron, Knightsen, and Bethel Island are unincorporated communities — remainder, not a second seat. Alameda is south — Oakland is that hall. Solano is north across the Strait — Fairfield is that hall.
This page is Side One for the place. The Sheriff’s job — opposite-coast remainder patrol and Martinez Detention / West County / Marsh Creek this badge still holds — is taught at Office of the Sheriff — Contra Costa County.
Five Supervisors at 1025 Escobar. They do not sit as the State Assembly.
Contra Costa is a general law county. A five-member Board of Supervisors, elected by district, sits at the County Administration Building, 1025 Escobar Street, Martinez, CA 94553. They fund roads, the Martinez courthouse campus, and the Sheriff’s budget. They do not hire the Sheriff. The people do. Concord City Council is a city body. Richmond City Council is a city body. The California Legislature sits in Sacramento. Alameda Board of Supervisors is a different county. None of those is this Board.
Contra Costa Superior Court lists the Wakefield Taylor Courthouse at 725 Court Street, Martinez (main), A.F. Bray at 1020 Ward Street, Spinetta Family Law Center at 751 Pine Street, George D. Carroll Courthouse at 100 37th Street, Richmond, Richard E. Arnason Justice Center at 1000 Center Drive, Pittsburg, and Walnut Creek Juvenile and Traffic at 640 Ygnacio Valley Road. Do not invent one Concord photograph as the whole map. Confirm live at contracosta.ca.gov and contracosta.courts.ca.gov.
The Sheriff is a county officer (California Constitution Article XI; Government Code § 24000). This Sheriff is not on the 2026 gubernatorial table. Elections Code § 1300 (AB 759, 2022) moved sheriff and district attorney to the presidential primary. A sheriff elected in 2022 serves a six-year term; the next regular is the 2028 presidential primary. Contra Costa has no charter that could have locked a gubernatorial-year date before 1 January 2021. Last regular 7 June 2022. Take office at noon on the first Monday after January 1 succeeding election (Gov. Code § 24200). The Governor is 2026. That is a different desk in Sacramento.
The Strait is water. Pittsburg is a city. Alameda is a different county.
Interstate 80, Interstate 680, and State Route 4 meet on this map. The Carquinez Strait and the Sacramento–San Joaquin Delta are water, not an Alameda badge. Mount Diablo is a mountain, not a second county. A refinery is industry — not this government, and not a reason to rewrite Alameda. Staff who paste a Concord photograph onto Escobar Street, or treat Richmond as the seat, or file Oakland as this county government, or rewrite this county as Autauga-with-a-strait, are on the wrong county.
How an opposite-coast public finds Escobar, Muir, Court Street, and Giant Highway
Board of Supervisors: 1025 Escobar Street, Martinez. Elections: 555 Escobar Street — contracostavote.gov. Sheriff Administration: 1850 Muir Road, Martinez, CA 94553 — (925) 655-0000. Martinez Detention Facility: 901 Court Street — (925) 335-4600. West County Detention Facility: 5555 Giant Highway, Richmond — (510) 262-4200. Marsh Creek Detention Facility: 12000 Marsh Creek Road, Clayton — (925) 646-5700. Wakefield Taylor Courthouse: 725 Court Street. Confirm live at cocosheriff.org and contracosta.ca.gov. A student who only knows a Concord photograph, or a Sacramento photograph as this county, or treats Richmond City Hall as Martinez Detention, has not found this campus.
Martinez Detention, West County, and Marsh Creek still jail. City PDs do not.
Crime in unincorporated Contra Costa — Bay Point, Rodeo, Crockett, El Sobrante, Pacheco, Alamo, Discovery Bay, and the remainder — is this Sheriff. Crime in Concord is often Concord Police. Crime in Richmond is often Richmond Police. Crime in Walnut Creek is often Walnut Creek Police. Crime in Antioch is often Antioch Police. This Sheriff is not those municipal departments. Martinez Detention Facility at 901 Court Street is primary intake. West County at 5555 Giant Highway is this Sheriff’s Richmond-side house — Richmond is still not the seat. Marsh Creek at 12000 Marsh Creek Road is still this Sheriff’s third house unless a live official door says otherwise. Official doors did not show a separate county Department of Corrections taking these houses — do not invent a jailer split.
CDCR is not this Sheriff. CHP is a state badge. BART Police is a transit badge. Kensington Police CSD is a district badge. Do not send a family looking for a county booking to Concord PD, to Richmond PD, or to Santa Rita (Alameda).
Care without inventing a refinery as this government
A peace order served in Bay Point. A court-ordered transport from 901 Court Street to 725 Court Street. A family visiting West County who lives in Hercules. Do not invent a church. Do not invent Concord as this oval. Do not invent Sacramento as this hall.
What Contra Costa actually watches
Court calendar on Wakefield Taylor, Carroll, Arnason, and Walnut Creek. A wreck on I-80. Fog on the Strait. High water in the Delta. Fire in the East Bay hills and on Diablo. Coordination with city PDs, CHP, and BART Police without becoming those departments. Coordination with Alameda’s Sheriff is mutual aid between two offices, not a merger. The Strait is geography. Concord is a city. Neither is Concord PD as this oval.
Martinez civic snapshot (verify official sources)
- State: California · County: Contra Costa · Seat: Martinez · Capital of California: Sacramento
- Map: Martinez · Concord · Richmond · Walnut Creek · Antioch · Pittsburg · Brentwood · Bay Point remainder · I-80 · I-680 · Highway 4 · the Strait · the Delta
- Not Concord as the hall · Not Richmond as the seat · Not the capital · Not city PD as this oval · Not Autauga-with-a-strait · Not Alameda-with-a-refinery
- Board: five Supervisors at 1025 Escobar Street
- Sheriff clock: not 2026 · last regular 2022 · next regular 2028 presidential primary · six-year bridge from AB 759
- Jails: Martinez Detention, 901 Court Street · West County, 5555 Giant Highway · Marsh Creek, 12000 Marsh Creek Road — this Sheriff still holds them (confirm Marsh Creek live)
Orientation adapted from the California Constitution Article XI, Elections Code § 1300, Government Code §§ 24000, 24200, 25304, and 26600, Contra Costa County official pages (contracosta.ca.gov, cocosheriff.org), Contra Costa Superior Court locations, and the Secretary of State for education. The Sheriff of record is whatever those sources say today. Confirm HQ versus court versus jail, and city PD versus this badge, on official pages before you travel.
What Martinez is not, as this county
- Not the capital of California. Sacramento is.
- Not Concord / Richmond / Walnut Creek / Antioch as the county government.
- Not Alameda. Not Los Angeles as this hall.
- Not Concord Police as this oval. Not Richmond / Walnut Creek / Antioch Police. Not CHP. Not BART Police.
- Not Santa Rita (Alameda). Not a Solano house.
- Not Autauga-with-a-strait. Not Alameda-with-a-refinery.
- Not the Governor (that desk is 2026 in Sacramento).
- Not a campaign flyer.