County profile · official public datasets

Blaine County, ID

96 public highway bridges tracked in the FHWA National Bridge Inventory: 25% rated Good, 71.9% Fair, 3.1% Poor.

96
Public bridges: 25%
Good condition: 3.1%
Poor condition

The verdict

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

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

Top 32%
lowest Poor share in state: 3.1%
Poor-condition share: 96
public highway bridges: 1978
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.

Blaine County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Blaine County ranks #14 of 44 Idaho counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 3.1%). Blaine County, Idaho contains 96 public highway bridges. Roughly 25% are rated “Good,” 71.9% “Fair,” and 3.1% “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 Blaine County

Good condition

25%

24 of 96 rated 7-9

Fair condition

71.9%

69 of 96 rated 5-6

Poor condition

3.1%

3 of 96 rated 4 or below

In-state Poor-share rank

#14 of 44

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

Condition distribution

Share of 96 NBI-tracked bridges by lowest applicable component rating.

Good

25% (24)

Fair

71.9% (69)

Poor

3.1% (3)

Blaine County's Poor-condition bridges carry 140 vehicle crossings a day

That is 0.1% of the county's reported daily bridge traffic on 3.1% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 47 crossings a day against 1,487 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 96 of 96 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

42.7% of Blaine County's bridges have passed the 50-year mark

41 of the 96 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 25% 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 42.9% of the county's Poor-condition bridge traffic

KILPATRICK BR. RD. over SILVER CREEK, built 1978, carries 60 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 3-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 140 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

20
1960s

6
1970s

26
1980s

10
1990s

15
2000s

6
2010s

5
2020s

3

What this shows Construction peaked in the 1970s, when 26 of the county's bridges still in the inventory were built, which is 27.1% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1978) matches the Idaho average (1979).

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

The 5 Idaho counties nearest Blaine County in number of bridges, with their condition splits. Its 3.1% Poor share is the 1st-lowest of these 6. Its average build year of 1978 against a peer-group mean of 1977 is in line with the group.

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

Bridge inventory size and condition shares for Blaine County and the 5 Idaho counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Bonner County	104	37.5%	53.8%	8.7%	1983
Elmore County	97	25.8%	70.1%	4.1%	1977
Blaine County (this page)	96	25%	71.9%	3.1%	1978
Boise County	88	46.6%	47.7%	5.7%	1978
Clearwater County	88	43.2%	51.1%	5.7%	1973
Adams County	87	32.2%	57.5%	10.3%	1975

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

Similar inventory size

Nearest county inventories outside ID (96 bridges here).

Del Norte County, CA · 96 bridges
Routt County, CO · 96 bridges
Clare County, MI · 96 bridges
Menominee County, MI · 96 bridges

Similar average build year

Nearest mean year-built outside ID (1978 here).

Orange County, CA · avg 1978 · 1,164 bridges
Sumner County, KS · avg 1978 · 659 bridges
Allen County, IN · avg 1978 · 613 bridges
Livingston County, IL · avg 1978 · 579 bridges

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

All 96 Good 24 Fair 69 Poor 3

All bridges (96)

Sort:

FOOTHILL LANE

Fair

Over: LITTLE WOOD RIVER

0.4 N. 0.7 W. CAREY, Blaine, ID

Built 1978 Load: 32.4 t ADT: 80

SH 75

Fair

Over: BELLEVUE CANAL

4.4 S. HAILEY, Blaine, ID

Built 1931 Load: 32.7 t ADT: 6,600

SH 75

Fair

Over: SMILEY CREEK

12.7 S. OBSIDIAN, Blaine, ID

Built 1977 Load: 32.7 t ADT: 750

SERENADE LANE

Fair

Over: TRAIL CREEK

0.6 S KETCHUM, Blaine, ID

Built 1995 Load: 32.7 t ADT: 500

US 93

Fair

Over: LITTLE WOOD RIVER

IN CAREY, Blaine, ID

Built 1977 Load: 34.5 t ADT: 2,700

US 20

Fair

Over: SILVER CREEK

8.9 W. CAREY, Blaine, ID

Built 1979 Load: 34.5 t ADT: 1,900

NORTH PICABO ROAD

Fair

Over: SILVER CREEK;N.PICABO B

0.6 N. PICABO, Blaine, ID

Built 1989 Load: 35.4 t ADT: 130

US 20

Fair

Over: ROCK CREEK

20.7 E. FAIRFIELD, Blaine, ID

Built 2019 Load: 35.6 t ADT: 2,100

SH 75

Fair

Over: RICHFIELD CANAL

18.7 N. SHOSHONE, Blaine, ID

Built 1955 Load: 36.3 t ADT: 4,500

ASPEN DRIVE

Fair

Over: WARM SPRINGS CREEK

0.7 N. 1.7 W. KETCHUM, Blaine, ID

Built 1991 Load: 36.9 t ADT: 390

SH 75

Fair

Over: BIG WOOD RIVER

6.7 N. KETCHUM, Blaine, ID

Built 1991 Load: 38.1 t ADT: 2,300

STC2810;GANNETT RD

Fair

Over: DISTRICT CANAL

1.1 S. 0.6 E. BELLEVUE, Blaine, ID

Built 1998 Load: 41.7 t ADT: 1,500

US 93

Fair

Over: LITTLE WOOD RIVER

3.3 SW. CAREY, Blaine, ID

Built 1987 Load: 44.5 t ADT: 860

PERO ROAD

Fair

Over: BELLEVUE CANAL

4.6 S. 1.6 E. BELLEVUE, Blaine, ID

Built 1993 Load: 44.5 t ADT: 100

OLD DOLLAR ROAD

Fair

Over: TRAIL CREEK

IN SUN VALLEY, Blaine, ID

Built 2004 Load: 46.3 t ADT: 1,000

SH 75

Fair

Over: BIG WOOD RIVER

0.6 S. KETCHUM SCL, Blaine, ID

Built 2017 Load: 48.9 t ADT: 14,000

CENARRUSA LANE

Fair

Over: LITTLE WOOD RIVER

0.6 S. 0.5 E. CAREY, Blaine, ID

Built 1940 Load: 80.7 t ADT: 35

AUSTIN ROAD

Fair

Over: FISH CREEK

3.3 N. 4.6 E. CAREY, Blaine, ID

Built 2009 Load: 91.6 t ADT: 30

GRIFFIN LP(NORTH)

Fair

Over: W.BR.LITTLE WOOD RIVER

1.6 S. 0.2 E. CAREY, Blaine, ID

Blaine County Bridge Snapshot

Condition distribution

Blaine County's Poor-condition bridges carry 140 vehicle crossings a day

42.7% of Blaine County's bridges have passed the 50-year mark

One structure carries 42.9% of the county's Poor-condition bridge traffic

How Blaine 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 (96)

FOOTHILL LANE

SH 75

SH 75

SERENADE LANE

US 93

US 20

NORTH PICABO ROAD

US 20

SH 75

ASPEN DRIVE

SH 75

STC2810;GANNETT RD

US 93

PERO ROAD

OLD DOLLAR ROAD

SH 75

CENARRUSA LANE

AUSTIN ROAD

GRIFFIN LP(NORTH)

FDR

FDR

STC2814;LTL WOOD

FDR

FDR

FDR

BROADFORD ROAD

US 20

ROAD

US 20

MULDOON CANYON RD

STC2822;GLENDALE R

ADAMS GULCH ROAD

GRIFFIN LOOP SOUTH

SH 75

FDR

STC2816;BULLION ST

SH 75

STC2822;GLENDALE R

SH 75

PRIEST ROAD

STC2822;GLENDALE R

US 20

DOLLAR ROAD

LTL WOOD RES. ROAD

KILPATRICK BR. RD.

PR

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