County profile · official public datasets

Cassia County, ID

116 public highway bridges tracked in the FHWA National Bridge Inventory: 15.5% rated Good, 84.5% Fair, 0% Poor.

116
Public bridges: 15.5%
Good condition: 0%
Poor condition

The verdict

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

Cassia County pairs a top-5% lowest Poor-condition share among rated counties in the state with a newer average build year than the state inventory.

Top 5%
lowest Poor share in state: 0%
Poor-condition share: 116
public highway bridges: 1984
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.

Cassia County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Cassia County ranks #2 of 44 Idaho counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 0%). Cassia County, Idaho contains 116 public highway bridges. Roughly 15.5% are rated “Good,” 84.5% “Fair,” and 0% “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

116

Public highway bridges in Cassia County

Good condition

15.5%

18 of 116 rated 7-9

Fair condition

84.5%

98 of 116 rated 5-6

Poor condition

0 of 116 rated 4 or below

In-state Poor-share rank

#2 of 44

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

Condition distribution

Share of 116 NBI-tracked bridges by lowest applicable component rating.

Good

15.5% (18)

Fair

84.5% (98)

Poor

0% (0)

39.7% of Cassia County's bridges have passed the 50-year mark

46 of the 116 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 15.5% 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.

1950s

3
1960s

27
1970s

31
1980s

18
1990s

7
2000s

14
2010s

10
2020s

6

What this shows Construction peaked in the 1970s, when 31 of the county's bridges still in the inventory were built, which is 26.7% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year is 1984, 5 years newer than the Idaho average of 1979.

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

The 5 Idaho counties nearest Cassia County in number of bridges, with their condition splits. Its 0% Poor share is the 1st-lowest of these 6. Its average build year of 1984 against a peer-group mean of 1979 is 5 years newer.

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

Bridge inventory size and condition shares for Cassia County and the 5 Idaho counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Twin Falls County	126	12.7%	84.1%	3.2%	1973
Bannock County	124	33.1%	62.1%	4.8%	1981
Cassia County (this page)	116	15.5%	84.5%	0%	1984
Latah County	115	35.7%	64.3%	0%	1978
Lemhi County	112	53.6%	40.2%	6.3%	1988
Jerome County	110	10%	80.9%	9.1%	1974

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

Similar inventory size

Nearest county inventories outside ID (116 bridges here).

Howard County, AR · 116 bridges
Worth County, IA · 116 bridges
Sheridan County, KS · 116 bridges
Caldwell County, KY · 116 bridges

Similar average build year

Nearest mean year-built outside ID (1984 here).

Hennepin County, MN · avg 1984 · 936 bridges
Duval County, FL · avg 1984 · 831 bridges
El Paso County, CO · avg 1984 · 686 bridges
Bell County, TX · avg 1984 · 660 bridges

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

All 116 Good 18 Fair 98 Poor 0

Fair-condition bridges (98)

Sort:

Cassia County Bridge Snapshot

Condition distribution

39.7% of Cassia County's bridges have passed the 50-year mark

How Cassia 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 (98)

COUNTY ROAD

I 86 EBL

I 86 WBL

I 84 EBL

I 84 EBL

I 84 WBL

50 WEST ROAD

STC 4698;E 600 N

SUBLETT ROAD

100 SOUTH ROAD

I 86 WBL

SH 77

I 84

950 EAST ROAD

500N-1130E

HEGLAR CANYON RD

I 86 EBL

SH 77

MAIN STREET(100 S)

STC2739;ROCK CR RD

I 86 EBL

950 EAST ROAD

I 86 WBL

SH 81

150 EAST ROAD

SH 77

I 84 EBL

SH 81B SPUR

STC 7552;PARK AVE

BEET DUMP ROAD

IDAHOME ROAD

SH 25

I 84

I 84 WBL

650 EAST ROAD

I 84 WBL

SH 81

I 86 EBL

I 84 EBL

SH 81

I 84B

I 84

150 EAST ROAD

950 EAST ROAD

STC4693;S 550 E

2950 EAST RD

W 1000 S

I 84

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