Marin County, CA

217 public highway bridges

Marin County Bridge Snapshot

Marin County, California contains 217 public highway bridges in the FHWA National Bridge Inventory. Roughly 34.6% are rated “Good,” 35% “Fair,” 8.3% “Poor,” and 8.3% are classified as structurally deficient — the federal designation for spans whose deck, superstructure, or substructure has been rated 4 or below on the 0–9 NBI scale. Structurally deficient does not mean unsafe to cross; it means the bridge is on the priority list for repair or replacement.

Inspections in CA are conducted by certified engineers from the state Department of Transportation on a 24-month cycle, and results are reported back to the FHWA each spring. The list below shows every NBI-tracked bridge in the county, sorted by inventory load rating. Use the “Sort by” controls to surface the lowest-rated spans first, and click any row for full inspection history, traffic counts, and condition trends.

Source: FHWA National Bridge Inventory. See methodology for full definitions.

217

Total Bridges

34.6%

Good

8.3%

Poor

8.3%

Structurally Deficient

Condition Distribution

Good

34.6% (75)

Fair

35% (76)

Poor

8.3% (18)

SD

8.3% (18)

All Bridges (217)

Sort:

U.S. HIGHWAY 101

Over: CORTE MADERA CR & SFD BL

04-MRN-101-8.47-LKSP, Marin, CA

Built 1957 ADT: 15,000

U.S. HIGHWAY 101

Over: CORTE MADERA CR & SFD BL

04-MRN-101-8.47-LKSP, Marin, CA

Built 1961 ADT: 32,990

U.S. HIGHWAY 101

Over: SR 1, RICH BY, FRNTGE RD

04-MRN-101-4.03-SAUS, Marin, CA

Built 1957 ADT: 30,500

N101-SAN PEDRO RD

Over: NORTH SAN PEDRO ROAD

04-MRN-101-12.69-SRF, Marin, CA

Built 1970 ADT: 16,800

U.S. HIGHWAY 101

Over: LINCOLN AVE-N101 ON RAMP

04-MRN-101-12.19-SRF, Marin, CA

Built 1938 ADT: 25,100

U.S. HIGHWAY 101

Over: LINDEN LANE

04-MRN-101-11.64-SRF, Marin, CA

Built 1947 ADT: 7,500

U.S. HIGHWAY 101

Over: 2ND, 3RD, 4TH, 5TH, MSSN

04-MRN-101-10.72-SRF, Marin, CA

Built 1965 ADT: 12,900

U. S. HIGHWAY 101

Over: 2ND, 3RD, 4TH, 5TH, MSSN

04-MRN-101-10.72-SRF, Marin, CA

Built 1941 ADT: 36,900

U.S. HIGHWAY 101

Over: SAUSALITO ROAD

04-MRN-101-0.32-SAUS, Marin, CA

Built 1935 ADT: 10,415

U.S. HIGHWAY 101

Over: DONAHUE ST/N. BRIDGE BLD

04-MRN-101-3.33-SAUS, Marin, CA

Built 1943 ADT: 5,920

PEDESTRIAN WALKWAY

Over: U.S. HIGHWAY 101

04-MRN-101-11.41-SRF, Marin, CA

Built 1969 ADT: 173,000

U.S. HIGHWAY 101

Over: LUCAS VALLEY ROAD

04-MRN-101-14.71-SRF, Marin, CA

Built 1952 ADT: 15,950

SB101-E580 CONNECT

Over: US HIGHWAY 101

04-MRN-101-9.94-SRF, Marin, CA

Built 2009 ADT: 165,000

WOLFBACK RIDGE RD

Over: U.S. HIGHWAY 101

04-MRN-101-1.52-SAUS, Marin, CA

Built 1954 ADT: 106,000

U.S. HIGHWAY 101

Over: US 101 ON & OFF RAMPS

04-MRN-101-1.68-SAUS, Marin, CA

Built 1954 ADT: 1,676

STATE ROUTE 131

Over: US HIGHWAY 101

04-MRN-131-0.01, Marin, CA

Built 1956 ADT: 133,000

TAMALPAIS DRIVE

Over: US HIGHWAY 101

04-MRN-101-7.37-CMAD, Marin, CA

Built 1957 ADT: 166,000

STATE ROUTE 580

Over: BELLAM BOULEVARD

04-MRN-580-4.50-SRF, Marin, CA

Built 1959 ADT: 29,468

STATE ROUTE 580

Over: BELLAM BOULEVARD

04-MRN-580-4.50-SRF, Marin, CA

Built 2010 ADT: 29,468

SIR FRAN DRAKE BLV

Over: STATE ROUTE 580

04-MRN-580-3.29-SRF, Marin, CA

Built 1957 ADT: 67,000

PEDESTRIAN WALKWAY

Over: U.S. HIGHWAY 101

04-MRN-101-4.75-CMAD, Marin, CA

Built 1957 ADT: 133,000

PEDESTRIAN WALKWAY

Over: U.S. HIGHWAY 101

04-MRN-101-8.29-LKSP, Marin, CA

Built 1959 ADT: 172,000

STATE ROUTE 37

Over: ATHERTON AVENUE

04-MRN-037-13.77, Marin, CA

Built 1959 ADT: 4,510

STATE ROUTE 37

Over: ATHERTON AVENUE

04-MRN-037-13.77, Marin, CA

Built 1959 ADT: 4,510

FREITAS PKWY

Over: U.S. HIGHWAY 101

04-MRN-101-13.71-SRF, Marin, CA

Built 1960 ADT: 1,700

W37-N101 CONNECTOR

Over: NOVATO BL-N101, NWP RR

04-MRN-037-R11.23-NVTO, Marin, CA

Built 1964 ADT: 3,800

W37-S101&N101 OFF

Over: COUNTY RD, US 101, NWPRR

04-MRN-037-R11.20-NVTO, Marin, CA

Built 1964 ADT: 900

MILLER CREEK ROAD

Over: U.S. HIGHWAY 101

04-MRN-101-15.57, Marin, CA

Built 1961 ADT: 5,000

IGNACIO BOULEVARD

Over: U.S. HIGHWAY 101

04-MRN-101-18.09-NVTO, Marin, CA

Built 1964 ADT: 5,000

CLAY ST / NAVE DR

Over: U.S. HIGHWAY 101

04-MRN-101-16.64-NVTO, Marin, CA

Built 1964 ADT: 150,000

S101-E37 & NOVATO-

Over: U.S. HIGHWAY 101

04-MRN-101-18.88-NVTO, Marin, CA

Built 1964 ADT: 143,000

S NOVATO BLVD

Over: W37-S101 CONNECTOR RAMP

04-MRN-101-18.94-NVTO, Marin, CA

Built 1964 ADT: 11,000

ROWLAND BOULEVARD

Over: U.S. HIGHWAY 101

04-MRN-101-R20.19-NVTO, Marin, CA

Built 1974 ADT: 123,000

DE LONG AVENUE

Over: U.S. HIGHWAY 101

04-MRN-101-R21.11-NVTO, Marin, CA

Built 1974 ADT: 123,000

U.S. HWY 101 SB

Over: OLIVE AVENUE

04-MRN-101-R21.47-NVTO, Marin, CA

Built 1974 ADT: 4,400

U.S. HWY 101 NB

Over: OLIVE AVENUE

04-MRN-101-R21.47-NVTO, Marin, CA

Built 1974 ADT: 4,400

ATHERTON AVENUE

Over: U.S. HIGHWAY 101

04-MRN-101-R22.00-NVTO, Marin, CA

Built 1974 ADT: 123,000

ROUTE 101 NB

Over: RUSH LANDING RD & NWP RR

04-MRN-101-R22.27-NVTO, Marin, CA

Built 1974 ADT: 2,000

N&S101-E37 CONNCTR

Over: S NOVATO BL,N101 & NWPRR

04-MRN-101-18.96-NVTO, Marin, CA

Built 1964 ADT: 800

MERRYDALE ROAD

Over: US 101 & MERRYDALE RD

04-MRN-101-13.50-SRF, Marin, CA

Built 1996 ADT: 167,000

S101 ON & OFF RAMP

Over: U.S. HIGHWAY 101

04-MRN-101-25.50, Marin, CA

Built 2006 ADT: 80,000

PEDESTRIAN BIKEWAY

Over: LINDEN LANE

04-MRN-000-0.00, Marin, CA

Built 2010 ADT: 7,500

PEDESTRIAN WALKWAY

Over: SIR FRANCIS DRAKE BLVD

1.4 MI W OF SR 101, Marin, CA

Built 1968 ADT: 10,000

PEDESTRIAN WALKWAY

Over: PARADISE DRIVE

INTX UPLAND CIRCLE INTRX, Marin, CA

Built 1970 ADT: 2,730

BIKE PATH

Over: BELLAM BLVD

UNDER U.S. HIGHWAY 101, Marin, CA

Built 1930 ADT: 2,500

PEDESTRIAN WALKWAY

Over: NICASIO VALLEY RD

0.15 MI N SIR FRNCS DK B2, Marin, CA

Built 1960 ADT: 1,330

PEDESTRIAN WALKWAY

Over: SIR FRANCIS DRAKE BLVD

1/4 MI E OF US 101, Marin, CA

Built 1981 ADT: 10,000

BIKE PATH

Over: SIR FRANCIS DRAKE BLVD

SAM P TAYLOR STATE PARK, Marin, CA

Built 1980 ADT: 2,500

HORSE CREEK CAMP R

Over: OLEMA CREEK

3.2 miles south of Olema,, Marin, CA

Built 1960 Load: 9.1 t ADT: 20

MILL CROSSING

Over: LAGUNITAS CREEK

SAMUEL P TAYLOR STATE PK, Marin, CA

Built 1947 Load: 10.4 t ADT: 1

Read our methodology — how this data is sourced, computed, and verified.

Related

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Data sourced from official U.S. government datasets. See our methodology for details. Retrieved and formatted by PlainBridges Editorial

Reviewed byPlainbridges Editorial, Plain Bridges Editorial Team · June 5, 2026