Total bridges
158
Public highway bridges in Napa County
County profile · official public datasets
Napa County, CA
158 public highway bridges tracked in the FHWA National Bridge Inventory: 45.6% rated Good, 50% Fair, 4.4% Poor.
- 158
- Public bridges
- 45.6%
- Good condition
- 4.4%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Napa County pairs a top-quartile lowest Poor-condition share among rated counties in the state with an older average build year than the state inventory.
- Top 24%
- lowest Poor share in state
- 4.4%
- Poor-condition share
- 158
- public highway bridges
- 1961
- avg year built
Poor is an FHWA condition category from the lowest applicable component rating (4 or below), not a live crossing-safety or closure decision. Rankings cover counties with at least five public highway bridges.
Napa County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Napa County ranks #14 of 58 California counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 4.4%). Napa County, California contains 158 public highway bridges. Roughly 45.6% are rated “Good,” 50% “Fair,” and 4.4% “Poor.” Poor means the lowest applicable deck, superstructure, substructure, or culvert rating is 4 or below on the 0–9 NBI scale. It is a condition category, not a live safety or closure decision.
Responsible agencies inspect covered bridges on risk-based intervals under current NBIS rules and submit inventory data to FHWA annually. The list below shows every NBI-tracked bridge in the county. Use the “Sort by” controls to change the ordering, and click any row for its reported inspection date, traffic count, and condition fields.
Source: FHWA National Bridge Inventory. See methodology for full definitions.
Good condition
45.6%
72 of 158 rated 7-9
Fair condition
50%
79 of 158 rated 5-6
Poor condition
4.4%
7 of 158 rated 4 or below
In-state Poor-share rank
#14 of 58
Among California counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 158 NBI-tracked bridges by lowest applicable component rating.
Good 45.6% (72)
Fair 50% (79)
Poor 4.4% (7)
Napa County's Poor-condition bridges carry 71,412 vehicle crossings a day
That is 5.5% of the county's reported daily bridge traffic on 4.4% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 10,202 crossings a day against 8,868 for a Good-condition one. A Poor rating is a condition category, not a closure or a live safety judgement; it means the lowest applicable component rating is 4 or below.
Computed over the 158 of 158 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
63.9% of Napa County's bridges have passed the 50-year mark
101 of the 158 bridges with a recorded construction year were built in 1974 or earlier. Age alone is not a defect: a well-maintained older bridge can rate Good, and 45.6% of this county's inventory does. Even so, this older cohort is the population from which future Poor ratings are drawn, which is why the age profile below matters alongside the condition split above.
Cutoff derives from the 2024 release year minus a 50-year design life. Source: FHWA National Bridge Inventory, 2024 release.
One structure carries 67.2% of the county's Poor-condition bridge traffic
STATE ROUTE 29 over NVRR NAPA RIVER STANLY, built 1977, carries 48,000 vehicles a day, the most of any Poor-rated structure here. The county's Poor-condition exposure is concentrated rather than evenly spread, so the 7-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 71,412 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Napa County's bridges were built
158 bridges with a recorded construction year, grouped by decade
- pre-1900 3
Built before 1900
3 bridges
- 1900s
1900–1909
11 bridges
- 1910s 7
1910–1919
7 bridges
- 1920s
1920–1929
12 bridges
- 1930s
1930–1939
17 bridges
- 1940s 7
1940–1949
7 bridges
- 1950s
1950–1959
13 bridges
- 1960s
1960–1969
18 bridges
- 1970s
1970–1979
18 bridges
- 1980s
1980–1989
18 bridges
- 1990s 7
1990–1999
7 bridges
- 2000s
2000–2009
11 bridges
- 2010s
2010–2019
11 bridges
- 2020s 5
2020–2029
5 bridges
What this shows Construction peaked in the 1960s, when 18 of the county's bridges still in the inventory were built, which is 11.4% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year is 1961, 9 years older than the California average of 1970.
How Napa County compares with California's closest counties by inventory size
The 5 California counties nearest Napa County in number of bridges, with their condition splits. Its 4.4% Poor share is the 2nd-lowest of these 6. Its average build year of 1961 against a peer-group mean of 1969 is 8 years older.
Showing the 5 closest of 57 California counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Kings County | 168 | 40.5% | 53.6% | 6% | 1968 |
| Plumas County | 165 | 26.7% | 69.1% | 4.2% | 1965 |
| Napa County (this page) | 158 | 45.6% | 50% | 4.4% | 1961 |
| San Francisco County | 143 | 34.3% | 51% | 14.7% | 1969 |
| Nevada County | 135 | 45.2% | 40.7% | 14.1% | 1972 |
| Lake County | 129 | 30.2% | 62% | 7.8% | 1970 |
Each share is of that county's own total tracked bridges; peers are the counties with 5 or more bridges whose inventory size is closest to Napa County's. Source: FHWA National Bridge Inventory, 2024 release.
Nationwide counties with similar inventory size or average build year
Two NBI-derived peer sets for Napa County, both outside California so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside CA (158 bridges here).
- Wells County, IN · 158 bridges
- Jackson County, MI · 158 bridges
- Yalobusha County, MS · 158 bridges
- Fergus County, MT · 158 bridges
Similar average build year
Nearest mean year-built outside CA (1961 here).
- Westchester County, NY · avg 1961 · 774 bridges
- Berkshire County, MA · avg 1961 · 450 bridges
- Schuylkill County, PA · avg 1961 · 368 bridges
- Columbiana County, OH · avg 1961 · 321 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Good-condition bridges (72)
REDWOOD ROAD
GoodOver: REDWOOD CREEK
AT DRY CREEK ROAD, Napa, CA
Built 1982 Load: 32.4 t ADT: 3,631
BROADWAY
GoodOver: AMERICAN CANYON CREEK
S/O AMERICAN CYN RD, Napa, CA
Built 1973 Load: 32.4 t ADT: 1,500
EVEY RD
GoodOver: NAPA RIVER
0.4 MI N BENNETT LANE, Napa, CA
Built 1980 Load: 32.4 t ADT: 64
VALLEYVIEW ST
GoodOver: SULPHUR CREEK
0.1 MI N GRAYSON AVE, Napa, CA
Built 1981 Load: 32.4 t ADT: 1,000
PETRIFIED FORST RD
GoodOver: CYRUS CREEK
0.5 MI W OF SR 128, Napa, CA
Built 1989 Load: 32.4 t ADT: 9,783
JEFFERSON ST
GoodOver: NAPA DRAIN
JUST NORTH OF TROWER AVE, Napa, CA
Built 1991 Load: 32.4 t ADT: 5,439
FIRST STREET
GoodOver: NAPA RIVER
0.1 MI W OF SR 121, Napa, CA
Built 2009 Load: 32.4 t ADT: 23,200
OAKVILLE CROSSROAD
GoodOver: NAPA RIVER
0.5 MI NE OF SR 29, Napa, CA
Built 2016 Load: 32.4 t ADT: 3,000
GREENWOOD AVE
GoodOver: NAPA RIVER
.2 MI SW/O MYRTLEDALE RD, Napa, CA
Built 2015 Load: 32.4 t ADT: 386
DEVLIN ROAD
GoodOver: FAGAN CREEK
0.1 MI N OF TOWER RD, Napa, CA
Built 2019 Load: 32.4 t ADT: 3,500
BERRY STREET
GoodOver: NAPA RIVER
SE OF WASHINGTON STREET, Napa, CA
Built 2018 Load: 32.4 t ADT: 1,500
MOUNT VEEDER ROAD
GoodOver: PICKLE CREEK
2.1 MILES N OF REDWOOD RD, Napa, CA
Built 2020 Load: 32.4 t ADT: 737
BERRYESSA-KNOXVLLE
GoodOver: ETICUERA CREEK
7.7 MI N/O POPE CYN ROAD, Napa, CA
Built 2020 Load: 32.4 t ADT: 370
GASSER DRIVE
GoodOver: TULOCAY CREEK
NORTH OF KANSAS AVE, Napa, CA
Built 2019 Load: 32.4 t ADT: 1,800
VILLA LANE
GoodOver: SILVERADO CREEK
0.35 MI N/O TRANCAS STR, Napa, CA
Built 1999 Load: 38.6 t ADT: 576
STATE ROUTE 29 SB
GoodOver: STATE RTE 121/IMOLA AVE
04-NAP-029-R10.38-NAP, Napa, CA
Built 1961 Load: 39.5 t ADT: 29,500
DEVLIN ROAD
GoodOver: SOSCOL CREEK
0.2 MI E SOSCOL FERRY RD, Napa, CA
Built 1981 Load: 44.4 t ADT: 499
MEADOWBROOK DRIVE
GoodOver: BROWNS VALLEY CREEK
JUST S OF TALL GRASS DR, Napa, CA
Built 2007 Load: 44.4 t ADT: 1
SR 121
GoodOver: SARCO CREEK
04-NAP-121-9.30, Napa, CA
Built 2018 Load: 47.3 t ADT: 12,000
TALL GRASS DRIVE
GoodOver: BROWNS VALLEY CREEK
JUST SOUTH OF PARTRICK RD, Napa, CA
Built 2009 Load: 68.7 t ADT: 1,000
SKYLARK WAY
GoodOver: BROWNS VALLEY CREEK
0.1M N OF TALL GRASS DR, Napa, CA
Built 2007 Load: 74.8 t ADT: 300
STATE ROUTE 128
GoodOver: WRAGG CREEK
04-NAP-128-27.90, Napa, CA
Built 1955 Load: 97.2 t ADT: 1,675
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.