County profile · official public datasets

Shoshone County, ID

260 public highway bridges tracked in the FHWA National Bridge Inventory: 21.5% rated Good, 68.8% Fair, 9.6% Poor.

260
Public bridges: 21.5%
Good condition: 9.6%
Poor condition

The verdict

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

Shoshone County pairs a higher-than-median Poor-condition share among rated counties in the state with an older average build year than the state inventory.

39th
of 44 on Poor share: 9.6%
Poor-condition share: 260
public highway bridges: 1971
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.

Shoshone County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Shoshone County ranks #39 of 44 Idaho counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 9.6%). Shoshone County, Idaho contains 260 public highway bridges. Roughly 21.5% are rated “Good,” 68.8% “Fair,” and 9.6% “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

260

Public highway bridges in Shoshone County

Good condition

21.5%

56 of 260 rated 7-9

Fair condition

68.8%

179 of 260 rated 5-6

Poor condition

9.6%

25 of 260 rated 4 or below

In-state Poor-share rank

#39 of 44

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

Condition distribution

Share of 260 NBI-tracked bridges by lowest applicable component rating.

Good

21.5% (56)

Fair

68.8% (179)

Poor

9.6% (25)

Shoshone County's Poor-condition bridges carry 18,060 vehicle crossings a day

That is 4.9% of the county's reported daily bridge traffic on 9.6% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 722 crossings a day against 837 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 260 of 260 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

58.5% of Shoshone County's bridges have passed the 50-year mark

152 of the 260 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 21.5% 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 46% of the county's Poor-condition bridge traffic

I 90 EBL & WBL over RR ROADBED/NO TRACKS, built 1972, carries 8,300 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 25-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 18,060 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

2
1910s

8
1930s

19
1940s

6
1950s

34
1960s

56
1970s

59
1980s

24
1990s

19
2000s

9
2010s

18
2020s

6

What this shows Construction peaked in the 1970s, when 59 of the county's bridges still in the inventory were built, which is 22.7% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year is 1971, 8 years older than the Idaho average of 1979.

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

The 5 Idaho counties nearest Shoshone County in number of bridges, with their condition splits. Its 9.6% Poor share is the 6th-lowest of these 6. Its average build year of 1971 against a peer-group mean of 1980 is 9 years older.

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

Bridge inventory size and condition shares for Shoshone County and the 5 Idaho counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Ada County	299	41.8%	58.2%	0%	1989
Canyon County	292	27.7%	69.5%	2.7%	1984
Bingham County	263	17.1%	79.5%	3.4%	1975
Shoshone County (this page)	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 Shoshone 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 Shoshone County, both outside Idaho so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside ID (260 bridges here).

Jefferson County, IL · 260 bridges
Mitchell County, KS · 260 bridges
Nash County, NC · 260 bridges
Trempealeau County, WI · 260 bridges

Similar average build year

Nearest mean year-built outside ID (1971 here).

Wayne County, MI · avg 1971 · 1,026 bridges
Baltimore County, MD · avg 1971 · 783 bridges
Washington County, PA · avg 1971 · 655 bridges
Linn County, OR · avg 1971 · 566 bridges

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

All 260 Good 56 Fair 179 Poor 25

Fair-condition bridges (179)

Sort:

Shoshone County Bridge Snapshot

Condition distribution

Shoshone County's Poor-condition bridges carry 18,060 vehicle crossings a day

58.5% of Shoshone County's bridges have passed the 50-year mark

One structure carries 46% of the county's Poor-condition bridge traffic

How Shoshone 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

Fair-condition bridges (179)

FS ROUTE NO. 301

FS ROUTE NO. 208

FS ROUTE NO. 1268

I 90 EBL

I 90 WBL

NORTH FRONTAGE RD

FS ROUTE NO. 338

I 90 EBL & WBL

STC5731;ST JOE RVR

I 90 EBL

I 90 WBL

CDA RIVER RD

I 90 EBL

I 90 WBL

I 90 WBL

FS ROUTE NO. 151

FS ROUTE NO. 320

I 90B LOOP

FS ROUTE NO. 812

I 90 EBL

FS ROUTE NO. 208

I 90B LOOP

FS ROUTE 301

SH 4

FS ROUTE NO. 208

STC5711;ST JOE RVR

WILLOW CREEK RD

STC 5711;MOON PASS

STC 5759;DIVISION

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