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State Route 37 over Petaluma River

Marin County, California · rated Fair in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

State Route 37 over Petaluma River in Marin County, California, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the substructure, rated 5 (fair condition) on the 0-9 scale.
It was built in 1958, making it 67 years old at the 2025 inventory.
It carries about 34,000 vehicles a day (traffic count year 2020).
Its listed owner is the state highway agency.
It is one of 100 of the 207 inventoried bridges in Marin County rated fair (48.3%); 16 (7.7%) are rated poor.
A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.

Component ratings


Structure	Steel stringer or multi-beam girder
Length	about 2,183 ft
Location	04-mrn-037-14.47
NBI structure number	27 0013
Condition class	Fair

Source: FHWA National Bridge Inventory, 2025 data as reported by the California department of transportation.

Bridge	Built	Vehicles/day	Condition
US Highway 101 over North San Pedro Road	1979	180,000	Fair
U.S. Highway 101 over Lincoln Ave-n101 on Ramp	1938	180,000	Fair
U.S. Highway 101 over Linden Lane	1947	173,000	Good
U.S. Highway 101 over Ggt Bellam Andersen	1958	172,000	Good
U.S. Highway 101 over Corte Madera CR & Sfd Bl	1957	172,000	Fair
U.S. Highway 101 over Wornum Drive	1929	172,000	Good