The area is said to have been covered by Pomo Native Americans before European intervention. The Russians first settled the area at Fort Ross as a fur-trading post, but the area was later settled by the Spanish-Mexican Alta California. The Bear Flag Revolt took place in the town of Sonoma, which is also the location of the last of the California Missions. General Mariano Guadalupe Vallejo, the last secretary to the Governor of California before its annexation to the United States, kept his home in Sonoma; his ranch, now a National Historic Location, was located in nearby Petaluma.
The North Bay remained isolated and rural well into the 20th Century. The opening of the Golden Gate Bridge in the 1930s transformed Marin County from a dairy farming region into an upscale suburban area. Until the 1990s, the region's growth was at a gradual pace, with significant restrictions on development being imposed in Marin and Napa Counties in the 1970s (future Senator Barbara Boxer was an important figure in the North Bay's open space preservation movement).