State Route 37 (SR 37) is a state highway in the northern part of California that runs 21 miles (34 km) along the northern shore of San Pablo Bay. It is built from U.S. Route 101 in Novato and runs through the southern tips of Sonoma and Napa counties to Interstate 80 in Vallejo. It serves as a vital connection between the four counties of the North Bay Area, north of San Francisco; Sonoma Raceway and Six Flags Discovery Kingdom are accessible from Route 37.