Explore Martinez local geography, civic resources and voter guides, with dated official population and registration facts for Contra Costa County.
At a glance: Martinez is an incorporated city in Contra Costa County. Population: 36,521 (California Department of Finance estimate as of January 1, 2026). Registered voters: 25,976 (California Secretary of State, as of September 4, 2026).
Martinez faces the Carquinez Strait at the mouth of the Alhambra Valley. Its downtown joins a working waterfront, railroad corridor, and county-government center, while neighborhoods climb into the surrounding hills. Waterfront Park and Rankin Park provide distinct recreation settings near the shoreline and inland hills. The city's parks resources include picnic-site maps and reservation information for these and other neighborhood parks. Martinez incorporated on April 1, 1876, and serves as the Contra Costa County seat. The municipal government is a general-law, council-manager organization, separate from the county offices located in the city.
No. Martinez is an incorporated city and the county seat, but municipal and county governments have separate responsibilities.
The city's Martinez Parks page provides site maps and recreation-division contact information.
Use Contra Costa County Elections for registration, ballots, and voting locations.
25,976 (California Secretary of State, as of September 4, 2026).
CA Slates began with shared voter guides in 2012 and expanded into its current publication family and connected program.