Total bridges
292
Public highway bridges in Canyon County
County profile · official public datasets
Canyon County, ID
292 public highway bridges tracked in the FHWA National Bridge Inventory: 27.7% rated Good, 69.5% Fair, 2.7% Poor.
- 292
- Public bridges
- 27.7%
- Good condition
- 2.7%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Canyon County pairs a top-quartile lowest Poor-condition share among rated counties in the state with a newer average build year than the state inventory.
- Top 23%
- lowest Poor share in state
- 2.7%
- Poor-condition share
- 292
- public highway bridges
- 1984
- 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.
Canyon County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Canyon County ranks #10 of 44 Idaho counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 2.7%). Canyon County, Idaho contains 292 public highway bridges. Roughly 27.7% are rated “Good,” 69.5% “Fair,” and 2.7% “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
27.7%
81 of 292 rated 7-9
Fair condition
69.5%
203 of 292 rated 5-6
Poor condition
2.7%
8 of 292 rated 4 or below
In-state Poor-share rank
#10 of 44
Among Idaho counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 292 NBI-tracked bridges by lowest applicable component rating.
Good 27.7% (81)
Fair 69.5% (203)
Poor 2.7% (8)
Canyon County's Poor-condition bridges carry 33,990 vehicle crossings a day
That is 1.5% of the county's reported daily bridge traffic on 2.7% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 4,249 crossings a day against 14,323 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 292 of 292 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
34.9% of Canyon County's bridges have passed the 50-year mark
102 of the 292 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 27.7% 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 58.8% of the county's Poor-condition bridge traffic
NHS 7773;10TH AVE over CITY ST;UPRR;CALDWELL OP, built 1956, carries 20,000 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 8-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 33,990 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Canyon County's bridges were built
292 bridges with a recorded construction year, grouped by decade
- 1910s 1
1910–1919
1 bridges
- 1920s 1
1920–1929
1 bridges
- 1930s 8
1930–1939
8 bridges
- 1940s 6
1940–1949
6 bridges
- 1950s 16
1950–1959
16 bridges
- 1960s
1960–1969
40 bridges
- 1970s
1970–1979
52 bridges
- 1980s
1980–1989
45 bridges
- 1990s
1990–1999
46 bridges
- 2000s
2000–2009
44 bridges
- 2010s 19
2010–2019
19 bridges
- 2020s 14
2020–2029
14 bridges
What this shows Construction peaked in the 1970s, when 52 of the county's bridges still in the inventory were built, which is 17.8% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year is 1984, 5 years newer than the Idaho average of 1979.
How Canyon County compares with Idaho's closest counties by inventory size
The 5 Idaho counties nearest Canyon County in number of bridges, with their condition splits. Its 2.7% Poor share is the 2nd-lowest of these 6. Its average build year of 1984 against a peer-group mean of 1977 is 7 years newer.
Showing the 5 closest of 43 Idaho counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Ada County | 299 | 41.8% | 58.2% | 0% | 1989 |
| Canyon County (this page) | 292 | 27.7% | 69.5% | 2.7% | 1984 |
| Bingham County | 263 | 17.1% | 79.5% | 3.4% | 1975 |
| Shoshone County | 260 | 21.5% | 68.8% | 9.6% | 1971 |
| Idaho County | 215 | 37.2% | 56.7% | 6% | 1975 |
| Bonneville County | 213 | 30.5% | 66.7% | 2.8% | 1977 |
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 Canyon 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 Canyon County, both outside Idaho so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside ID (292 bridges here).
- Hancock County, IL · 292 bridges
- Logan County, IL · 292 bridges
- Jackson County, OK · 292 bridges
- Clearfield County, PA · 292 bridges
Similar average build year
Nearest mean year-built outside ID (1984 here).
- Hennepin County, MN · avg 1984 · 936 bridges
- Duval County, FL · avg 1984 · 831 bridges
- El Paso County, CO · avg 1984 · 686 bridges
- Bell County, TX · avg 1984 · 660 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Poor-condition bridges (8)
ROSE GARDEN RD
PoorOver: NOTUS CANAL
CALDWELL;ROSE GARDEN RD, Canyon, ID
Built 1935 Load: 10.9 t ADT: 600
NHS 7773;10TH AVE
PoorOver: CITY ST;UPRR;CALDWELL OP
IN CALDWELL;10TH AVE, Canyon, ID
Built 1956 Load: 16.3 t ADT: 20,000
14TH AVE N.
PoorOver: INDIAN CREEK
IN NAMPA;14TH AVE.N., Canyon, ID
Built 1947 Load: 22.7 t ADT: 930
STC 7787;PLYMOUTH
PoorOver: BOISE RIVER & CANAL
CALDWELL NCL, Canyon, ID
Built 1922 Load: 24.5 t ADT: 2,000
STC 3851;HEXON RD
PoorOver: BOISE RIVER
0.4 S. 1.2 W. PARMA, Canyon, ID
Built 1954 Load: 24.5 t ADT: 560
I 84 WB ON RAMP
PoorOver: BOISE RIVER;RAMP DA BR
IN CALDWELL, Canyon, ID
Built 1980 Load: 27.2 t ADT: 5,000
SMA 7733;KIMBALL A
PoorOver: INDIAN CREEK
IN CALDWELL;S.KIMBALL AVE, Canyon, ID
Built 1933 Load: 37.2 t ADT: 3,500
STC7165;FARMWAY RD
PoorOver: FARMERS COOP SEBREE CNL
1.7 S. 4.2 E. NOTUS, Canyon, ID
Built 1999 Load: 55.3 t ADT: 1,400
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.