Martinez is a city in Contra Costa County, California, located on the southern shore of the Carquinez Strait in the East Bay region of the San Francisco Bay Area. It is the county seat and had a population of 37,287 at the 2020 census. The city was founded on Rancho El Pinole, owned by Californio ranchero Ygnacio Martínez, and is known for its historic downtown and waterfront.
Historically, the area was inhabited by the Karkines, part of the Ohlone Indians. Martinez developed during the Gold Rush as a way station and became the county seat in 1850. Key historic sites include the Vicente Martinez Adobe (1849) and the John Muir National Historic Site. The city played a role in the Pony Express and early ferry service across the Carquinez Strait.Martinez became an important petroleum center in the early 20th century, with oil refineries established by companies including Pacific Coast Oil (later Standard Oil), Shell, and Golden Eagle. Some facilities are still operational today, such as the Shell refinery (owned by PBF Energy). Local folklore also claims that the Martini cocktail was invented in Martinez.









