County profile · official public datasets

Boundary County, ID

83 public highway bridges tracked in the FHWA National Bridge Inventory: 32.5% rated Good, 57.8% Fair, 9.6% Poor.

83
Public bridges: 32.5%
Good condition: 9.6%
Poor condition

The verdict

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

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

40th
of 44 on Poor share: 9.6%
Poor-condition share: 83
public highway bridges: 1982
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.

Boundary County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Boundary County ranks #40 of 44 Idaho counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 9.6%). Boundary County, Idaho contains 83 public highway bridges. Roughly 32.5% are rated “Good,” 57.8% “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

Public highway bridges in Boundary County

Good condition

32.5%

27 of 83 rated 7-9

Fair condition

57.8%

48 of 83 rated 5-6

Poor condition

9.6%

8 of 83 rated 4 or below

In-state Poor-share rank

#40 of 44

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

Condition distribution

Share of 83 NBI-tracked bridges by lowest applicable component rating.

Good

32.5% (27)

Fair

57.8% (48)

Poor

9.6% (8)

Boundary County's Poor-condition bridges carry 1,440 vehicle crossings a day

That is 2.3% 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 180 crossings a day against 197 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 83 of 83 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

39.8% of Boundary County's bridges have passed the 50-year mark

33 of the 83 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 32.5% 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 61.1% of the county's Poor-condition bridge traffic

S5907;DEEP CRK LP over BNRR;UPRR & DEEP CREEK, built 1936, carries 880 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 1,440 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1920s

1
1930s

1
1950s

9
1960s

14
1970s

19
1980s

12
1990s

4
2000s

10
2010s

8
2020s

5

What this shows Construction peaked in the 1970s, when 19 of the county's bridges still in the inventory were built, which is 22.9% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1982) matches the Idaho average (1979).

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

The 5 Idaho counties nearest Boundary County in number of bridges, with their condition splits. Its 9.6% Poor share is the 5th-lowest of these 6. Its average build year of 1982 against a peer-group mean of 1976 is 6 years newer.

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

Bridge inventory size and condition shares for Boundary County and the 5 Idaho counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Boise County	88	46.6%	47.7%	5.7%	1978
Adams County	87	32.2%	57.5%	10.3%	1975
Boundary County (this page)	83	32.5%	57.8%	9.6%	1982
Gooding County	80	16.3%	76.3%	7.5%	1965
Madison County	80	30%	70%	0%	1981
Washington County	80	32.5%	61.3%	6.3%	1979

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

Similar inventory size

Nearest county inventories outside ID (83 bridges here).

Desha County, AR · 83 bridges
Little River County, AR · 83 bridges
Wayne County, GA · 83 bridges
Waseca County, MN · 83 bridges

Similar average build year

Nearest mean year-built outside ID (1982 here).

Oklahoma County, OK · avg 1982 · 1,216 bridges
Jackson County, MO · avg 1982 · 930 bridges
Milwaukee County, WI · avg 1982 · 893 bridges
Champaign County, IL · avg 1982 · 727 bridges

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

All 83 Good 27 Fair 48 Poor 8

All bridges (83)

Sort:

Boundary County Bridge Snapshot

Condition distribution

Boundary County's Poor-condition bridges carry 1,440 vehicle crossings a day

39.8% of Boundary County's bridges have passed the 50-year mark

One structure carries 61.1% of the county's Poor-condition bridge traffic

How Boundary 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 (83)

FS ROUTE NO. 2443

STAGECOACH ROAD

FS ROUTE NO. 448

OLD ADDIE ROAD

FS ROUTE NO. 633

HELLROARING RIDGE

FS ROUTE NO. 2549

FS ROUTE NO. 2567

FS ROUTE NO. 1309

FS ROUTE NO. 435

FS ROUTE #2646

TWENTY MILE CR RD

FS ROUTE 633

DEER CREEK ROAD

RUBY CREEK ROAD

R0AD

STC5907;DEEP CRK

STC5907;DEEP CREEK

US 95

STC 5804;LIONS DEN

FS ROUTE NO. 1007

FS ROUTE 281

STC 5804;WESTSIDE

RUBY CREEK RD

US 95

FS ROUTE NO. 2450

FS ROUTE NO 2546

WILDERNESS ROAD

S5907;DEEP CRK LP

STC 5804;WESTSIDE

FS ROUTE NO. 427

RUBY CREEK RD

FS ROUTE NO. 1009

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