County profile · official public datasets

Clark County, ID

40 public highway bridges tracked in the FHWA National Bridge Inventory: 22.5% rated Good, 65% Fair, 12.5% Poor.

40
Public bridges: 22.5%
Good condition: 12.5%
Poor condition

The verdict

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

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

43rd
of 44 on Poor share: 12.5%
Poor-condition share: 40
public highway bridges: 1977
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.

Clark County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Clark County ranks #43 of 44 Idaho counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 12.5%). Clark County, Idaho contains 40 public highway bridges. Roughly 22.5% are rated “Good,” 65% “Fair,” and 12.5% “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 Clark County

Good condition

22.5%

9 of 40 rated 7-9

Fair condition

65%

26 of 40 rated 5-6

Poor condition

12.5%

5 of 40 rated 4 or below

In-state Poor-share rank

#43 of 44

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

Condition distribution

Share of 40 NBI-tracked bridges by lowest applicable component rating.

Good

22.5% (9)

Fair

65% (26)

Poor

12.5% (5)

Clark County's Poor-condition bridges carry 2,260 vehicle crossings a day

That is 5.9% of the county's reported daily bridge traffic on 12.5% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 452 crossings a day against 275 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 40 of 40 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

62.5% of Clark County's bridges have passed the 50-year mark

25 of the 40 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 22.5% 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 77.4% of the county's Poor-condition bridge traffic

I 15 NBL over HUMPHREY ROAD IC, built 1966, carries 1,750 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 5-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 2,260 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1930s

2
1940s

1
1950s

4
1960s

13
1970s

5
1980s

1
1990s

4
2000s

5
2010s

4
2020s

1

What this shows Construction peaked in the 1960s, when 13 of the county's bridges still in the inventory were built, which is 32.5% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1977) matches the Idaho average (1979).

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

The 5 Idaho counties nearest Clark County in number of bridges, with their condition splits. Its 12.5% Poor share is the 6th-lowest of these 6. Its average build year of 1977 against a peer-group mean of 1983 is 6 years older.

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

Bridge inventory size and condition shares for Clark County and the 5 Idaho counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Owyhee County	48	31.3%	60.4%	8.3%	1975
Benewah County	47	21.3%	74.5%	4.3%	1978
Caribou County	45	26.7%	66.7%	6.7%	1985
Clark County (this page)	40	22.5%	65%	12.5%	1977
Teton County	37	43.2%	51.4%	5.4%	1992
Bear Lake County	34	41.2%	58.8%	0%	1985

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

Similar inventory size

Nearest county inventories outside ID (40 bridges here).

Taliaferro County, GA · 40 bridges
St. John the Baptist County, LA · 40 bridges
Douglas County, MN · 40 bridges
Mahnomen County, MN · 40 bridges

Similar average build year

Nearest mean year-built outside ID (1977 here).

San Diego County, CA · avg 1977 · 1,632 bridges
King County, WA · avg 1977 · 1,238 bridges
Riverside County, CA · avg 1977 · 1,117 bridges
Shelby County, TN · avg 1977 · 1,077 bridges

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

All 40 Good 9 Fair 26 Poor 5

Fair-condition bridges (26)

Sort:

Clark County Bridge Snapshot

Condition distribution

Clark County's Poor-condition bridges carry 2,260 vehicle crossings a day

62.5% of Clark County's bridges have passed the 50-year mark

One structure carries 77.4% of the county's Poor-condition bridge traffic

How Clark 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 (26)

GRAVY RIDGE ROAD

OLD HWY 91

DIVERSION ROAD

2ND SOUTH ST

SKULL CANYON ROAD

SH 28

STC6805;A-2 CLK CO

I 15

STC6805;A-2 CLK CO

JENSEN LANE

SHENTON RD

STC6805;A-2 CLK CO

STC 6862;MAIN ST

I 15 NBL

I 15 SBL

I 15 NBL

I 15 SBL

I 15

I 15 NBL

SH 28

SH 28

I 15 SBL

I 15

I 15 SBL

I 15 NBL & SBL

I 15

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