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.

Total bridges

112

Public highway bridges in Lemhi County

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.

1920s

1
1930s

3
1940s

1
1950s

11
1960s

15
1970s

18
1980s

6
1990s

9
2000s

9
2010s

38
2020s

1

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.

Bridge inventory size and condition shares for Lemhi County and the 5 Idaho counties closest to it in inventory size
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.

All 112 Good 60 Fair 45 Poor 7

All bridges (112)

Sort:

Lemhi County Bridge Snapshot

Condition distribution

Lemhi County's Poor-condition bridges carry 1,185 vehicle crossings a day

37.5% of Lemhi County's bridges have passed the 50-year mark

One structure carries 29.5% of the county's Poor-condition bridge traffic

How Lemhi 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 (112)

PETERSON RANCH RD

CARMEN CREEK ROAD

LEMHI ROAD

MABEY LANE

S DAISY STREET

STC 6876;HAYDEN CR

COTTOM LANE

FDR 60103

NO DATA ENTERED

NO DATA ENTERED

ROAD

US 93

LEMHI RD;OLD HWY28

NO DATA ENTERED

INDIAN CREEK RD

FSR 60055

FDR 61000

NO DATA ENTERED

FDR 60099

NO DATA ENTERED

YELLOWJACKET ROAD

NO DATA ENTERED

NO DATA ENTERED

NO DATA ENTERED

NO DATA ENTERED

INDIAN CREEK RD

BEAR VALLEY CR. RD

NO DATA ENTERED

NO DATA ENTERED

US 93

US 93

INDIAN CREEK RD

US 93

US 93

US 93

STC6870;PAHSIMEROI

NO DATA ENTERED

IRON CREEK ROAD

BARRACKS LANE

SH 29

IDFG ACCESS ROAD

SH 28

RINGBONE MINE RD.

SH 28

SH 28

DEEP CR. ROAD

SHEEP CR. ROAD

NO DATA ENTERED

MAIERS LANE

3043: WARM SPRING

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