Vallejo, California is in the United States.
California ( [ kælᵻˈfɔːrnjə , _ - ni.ə ] , ) is the most populous state in the United States and the third most extensive by area . The North Bay is a subregion of the San Francisco Bay Area , in California , United States . Vallejo ( [ vəˈleɪ.oʊ , _ - hoʊ ] ; Spanish : [ baˈʎexo ] ) is a waterfront port city in Solano County , California , located in the North Bay region of the San Francisco Bay Area .