It is in Contra Costa County and is spelled without the added 'h' as Pittsburg. It once had the 'h' just as it also had various other names including:
Oakland, California is in Alameda County.
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Folsom, CA is part of Sacramento County. It is located at the northeastern corner of the county and adjoins Placer county to the west and El Dorado county to the east. The top borders extends into Folsom Lake.
Fullerton, CA is located in Orange county.
Berkeley, CA is located in Alameda county.
Cypress, CA is located in Orange county.
Fresno is the county seat in the county of Fresno located in the state of CA. The capital of CA is Sacramento.
Fresno is the county seat of Fresno County located in central CA in the San Joaquin Valley.
Costa Mesa, CA is located in Orange county.
Baldwin Hills, CA is located in Los Angeles County.
Fountain Valley, CA is located in Orange county.
Buena Park, CA is located in Orange county.