Total bridges
112
Public highway bridges in Lemhi County
County profile · official public datasets
Lemhi County, ID
112 public highway bridges tracked in the FHWA National Bridge Inventory: 53.6% rated Good, 40.2% Fair, 6.3% Poor.
- 112
- Public bridges
- 53.6%
- Good condition
- 6.3%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Lemhi County pairs a higher-than-median Poor-condition share among rated counties in the state with a newer average build year than the state inventory.
- 29th
- of 44 on Poor share
- 6.3%
- Poor-condition share
- 112
- public highway bridges
- 1988
- 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.
Lemhi County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Lemhi County ranks #29 of 44 Idaho counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.3%). Lemhi County, Idaho contains 112 public highway bridges. Roughly 53.6% are rated “Good,” 40.2% “Fair,” and 6.3% “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
53.6%
60 of 112 rated 7-9
Fair condition
40.2%
45 of 112 rated 5-6
Poor condition
6.3%
7 of 112 rated 4 or below
In-state Poor-share rank
#29 of 44
Among Idaho counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 112 NBI-tracked bridges by lowest applicable component rating.
Good 53.6% (60)
Fair 40.2% (45)
Poor 6.3% (7)
Lemhi County's Poor-condition bridges carry 1,185 vehicle crossings a day
That is 2.9% of the county's reported daily bridge traffic on 6.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 169 crossings a day against 269 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 112 of 112 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
37.5% of Lemhi County's bridges have passed the 50-year mark
42 of the 112 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 53.6% 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 29.5% of the county's Poor-condition bridge traffic
SALMON RIVER ROAD over PINE CREEK, built 2012, carries 350 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 1,185 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Lemhi County's bridges were built
112 bridges with a recorded construction year, grouped by decade
- 1920s 1
1920–1929
1 bridges
- 1930s 3
1930–1939
3 bridges
- 1940s 1
1940–1949
1 bridges
- 1950s 11
1950–1959
11 bridges
- 1960s 15
1960–1969
15 bridges
- 1970s
1970–1979
18 bridges
- 1980s 6
1980–1989
6 bridges
- 1990s 9
1990–1999
9 bridges
- 2000s 9
2000–2009
9 bridges
- 2010s
2010–2019
38 bridges
- 2020s 1
2020–2029
1 bridges
What this shows Construction peaked in the 2010s, when 38 of the county's bridges still in the inventory were built, which is 33.9% of those with a recorded year. That cohort is now 5 to 14 years old in the 2024 inventory. Its average build year is 1988, 9 years newer than the Idaho average of 1979.
How Lemhi County compares with Idaho's closest counties by inventory size
The 5 Idaho counties nearest Lemhi County in number of bridges, with their condition splits. Its 6.3% Poor share is the 4th-lowest of these 6. Its average build year of 1988 against a peer-group mean of 1980 is 8 years newer.
Showing the 5 closest of 43 Idaho counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Bannock County | 124 | 33.1% | 62.1% | 4.8% | 1981 |
| Cassia County | 116 | 15.5% | 84.5% | 0% | 1984 |
| Latah County | 115 | 35.7% | 64.3% | 0% | 1978 |
| Lemhi County (this page) | 112 | 53.6% | 40.2% | 6.3% | 1988 |
| Jerome County | 110 | 10% | 80.9% | 9.1% | 1974 |
| Bonner County | 104 | 37.5% | 53.8% | 8.7% | 1983 |
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 Lemhi 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 Lemhi County, both outside Idaho so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside ID (112 bridges here).
- Columbia County, FL · 112 bridges
- Sumter County, FL · 112 bridges
- Houston County, GA · 112 bridges
- Tift County, GA · 112 bridges
Similar average build year
Nearest mean year-built outside ID (1988 here).
- Travis County, TX · avg 1988 · 1,544 bridges
- Grant County, OK · avg 1988 · 476 bridges
- Loudoun County, VA · avg 1988 · 442 bridges
- Licking County, OH · avg 1988 · 439 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Poor-condition bridges (7)
VIOLA LANE
PoorOver: LEMHI RIVER(BAGLEY BR)
0.1 S. 0.2 W. TENDOY, Lemhi, ID
Built 1991 Load: 11.8 t ADT: 50
N. ST. CHARLES
PoorOver: LEMHI RIVER
0.4 N. 0.3 E. SALMON, Lemhi, ID
Built 1948 Load: 16.3 t ADT: 310
NO DATA ENTERED
PoorOver: PANTHER CREEK
NO DATA ENTERED, Lemhi, ID
Built 1980 Load: 17.2 t ADT: 200
MOCCASIN-NAPIAS RD
PoorOver: NAPIAS CREEK
NO DATA ENTERED, Lemhi, ID
Built 1953 Load: 24.3 t ADT: 25
NO DATA ENTERED
PoorOver: YELLOWJACKET CREEK
NO DATA ENTERED, Lemhi, ID
Built 1962 Load: 29.8 t ADT: 50
NO DATA ENTERED
PoorOver: BOULDER CREEK
NO DATA ENTERED, Lemhi, ID
Built 1966 Load: 35.3 t ADT: 200
SALMON RIVER ROAD
PoorOver: PINE CREEK
PINE CREEK, Lemhi, ID
Built 2012 Load: 37.3 t ADT: 350
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.