County profile · official public datasets

Idaho County, ID

215 public highway bridges tracked in the FHWA National Bridge Inventory: 37.2% rated Good, 56.7% Fair, 6% Poor.

215
Public bridges: 37.2%
Good condition: 6%
Poor condition

The verdict

According to the Federal Highway Administration's 2024 National Bridge Inventory.

Idaho County posts a higher-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.

28th
of 44 on Poor share: 6%
Poor-condition share: 215
public highway bridges: 1975
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.

Idaho County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Idaho County ranks #28 of 44 Idaho counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6%). Idaho County, Idaho contains 215 public highway bridges. Roughly 37.2% are rated “Good,” 56.7% “Fair,” and 6% “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.

Total bridges

215

Public highway bridges in Idaho County

Good condition

37.2%

80 of 215 rated 7-9

Fair condition

56.7%

122 of 215 rated 5-6

Poor condition

13 of 215 rated 4 or below

In-state Poor-share rank

#28 of 44

Among Idaho counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 215 NBI-tracked bridges by lowest applicable component rating.

Good

37.2% (80)

Fair

56.7% (122)

Poor

6% (13)

Idaho County's Poor-condition bridges carry 2,339 vehicle crossings a day

That is 3.2% of the county's reported daily bridge traffic on 6% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 180 crossings a day against 242 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 215 of 215 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

59.5% of Idaho County's bridges have passed the 50-year mark

128 of the 215 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 37.2% 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 47% of the county's Poor-condition bridge traffic

SH 162 over SEVEN MILE CREEK, built 1949, carries 1,100 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 13-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 2,339 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1920s

3
1930s

14
1940s

4
1950s

30
1960s

63
1970s

26
1980s

13
1990s

15
2000s

18
2010s

27
2020s

2

What this shows Construction peaked in the 1960s, when 63 of the county's bridges still in the inventory were built, which is 29.3% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1975) matches the Idaho average (1979).

How Idaho County compares with Idaho's closest counties by inventory size

The 5 Idaho counties nearest Idaho County in number of bridges, with their condition splits. Its 6% Poor share is the 4th-lowest of these 6. Its average build year of 1975 against a peer-group mean of 1978 is in line with the group.

Showing the 5 closest of 43 Idaho counties eligible for comparison.

Bridge inventory size and condition shares for Idaho County and the 5 Idaho counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Bingham County	263	17.1%	79.5%	3.4%	1975
Shoshone County	260	21.5%	68.8%	9.6%	1971
Idaho County (this page)	215	37.2%	56.7%	6%	1975
Bonneville County	213	30.5%	66.7%	2.8%	1977
Kootenai County	154	31.2%	65.6%	3.2%	1984
Valley County	149	45%	48.3%	6.7%	1982

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 Idaho 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 Idaho County, both outside Idaho so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside ID (215 bridges here).

Lawrence County, AL · 215 bridges
Terrebonne County, LA · 215 bridges
Marshall County, MN · 215 bridges
Washington County, OK · 215 bridges

Similar average build year

Nearest mean year-built outside ID (1975 here).

San Bernardino County, CA · avg 1975 · 1,422 bridges
Lane County, OR · avg 1975 · 1,010 bridges
Fulton County, GA · avg 1975 · 775 bridges
Westmoreland County, PA · avg 1975 · 620 bridges

Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.

All 215 Good 80 Fair 122 Poor 13

All bridges (215)

Sort:

Idaho County Bridge Snapshot

Condition distribution

Idaho County's Poor-condition bridges carry 2,339 vehicle crossings a day

59.5% of Idaho County's bridges have passed the 50-year mark

One structure carries 47% of the county's Poor-condition bridge traffic

How Idaho County compares with Idaho's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

All bridges (215)

FOREST ROAD 1172

NO DATA ENTERED

STC 4707;OLD HWY95

FOREST ROAD 492

LONGHAUL ROAD

SAVAGE PASS ROAD

BIG SALMON ROAD

FRD 5956

NO DATA ENTERED

FDR 103

FOREST ROAD 440A

STC 4719;RED RIVER

WHITE BIRD RIDGE

STC4702;SALMON RVR

NO DATA ENTERED

NO DATA ENTERED

FOREST ROAD 309

NO DATA ENTERED

US 95

NO DATA ENTERED

COMPOUND ROAD

LOLO CREEK ROAD

ROAD 492

NO DATA ENTERED

FSR 107

US 12

STC 4710;ROCKY CYN

NFSR 223

STC 4715;CLEAR CRK

FOREST ROAD 1858

ZUMWALT ROAD

ELK CREEK ROAD

FDR 103

NO DATA ENTERED

NFSR 50246

STC4713;WDLAND GRD

US 12

US 12

US 12

US 95

SH 14

NO DATA ENTERED

STC4710;GRAVES CRK

SH 13

FDR 369

STC 4719;DIXIE Rd

SH 13

STEAMBOAT ROAD

GROUSE CR-MARSHAL

STC 4709;WHITEBIRD

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