California State Route 37

State Route 37
SR 37 highlighted in red
Route information
Maintained by Caltrans
Length	21.494 mi[1] (34.591 km)
Existed	1917[2] 1934–present
Major junctions
West end	US 101 in Novato
Major intersections	SR 121 at Sears Point SR 29 in Vallejo
East end	I-80 in Vallejo
Location
Country	United States
State	California
Counties	Marin, Sonoma, Solano
Highway system
State highways in California Interstate US State Scenic History Pre‑1964 Unconstructed Deleted Freeways
← SR 36 → SR 38

State Route 37 (SR 37) is a state highway in the U.S. state of California that runs 21 miles (34 km) along the northern shore of San Pablo Bay. It serves as a vital connection in the North Bay region of the San Francisco Bay Area, running from U.S. Route 101 in Novato, through northeastern Marin County, and the southern tips of both Sonoma and Solano Counties to Interstate 80 in Vallejo. Sonoma Raceway and Six Flags Discovery Kingdom are accessible from Highway 37.

The section of Highway 37 between Sears Point and Vallejo was the Sears Point Toll Road, a toll road managed by Golden Gate Ferry, before it was purchased by the State in 1938. The highway has been proposed to be built to freeway standards since the early 1950s. However, the proposal was met with many economic and environmental obstacles, making the task all but impossible for much of the route. The route is plagued by flooding which can be exacerbated by levee breaks near Vallejo. Most of the highway crosses a marsh that is home to endangered salt marsh harvest mice. A section of highway was once known as "Blood Alley" for its high rate of fatal accidents. A concrete barrier built in the 1990s eliminated those fatal head-on collisions. By 2022, there have been proposals to reinstate tolls between Sears Point and Vallejo to help pay for flooding and other improvements.