County profile · official public datasets

Canyon County, ID

292 public highway bridges tracked in the FHWA National Bridge Inventory: 27.7% rated Good, 69.5% Fair, 2.7% Poor.

292
Public bridges: 27.7%
Good condition: 2.7%
Poor condition

The verdict

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

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

Top 23%
lowest Poor share in state: 2.7%
Poor-condition share: 292
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.

Canyon County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Canyon County ranks #10 of 44 Idaho counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 2.7%). Canyon County, Idaho contains 292 public highway bridges. Roughly 27.7% are rated “Good,” 69.5% “Fair,” and 2.7% “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

292

Public highway bridges in Canyon County

Good condition

27.7%

81 of 292 rated 7-9

Fair condition

69.5%

203 of 292 rated 5-6

Poor condition

2.7%

8 of 292 rated 4 or below

In-state Poor-share rank

#10 of 44

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

Condition distribution

Share of 292 NBI-tracked bridges by lowest applicable component rating.

Good

27.7% (81)

Fair

69.5% (203)

Poor

2.7% (8)

Canyon County's Poor-condition bridges carry 33,990 vehicle crossings a day

That is 1.5% of the county's reported daily bridge traffic on 2.7% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 4,249 crossings a day against 14,323 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 292 of 292 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

34.9% of Canyon County's bridges have passed the 50-year mark

102 of the 292 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 27.7% 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 58.8% of the county's Poor-condition bridge traffic

NHS 7773;10TH AVE over CITY ST;UPRR;CALDWELL OP, built 1956, carries 20,000 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 33,990 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

1
1920s

1
1930s

8
1940s

6
1950s

16
1960s

40
1970s

52
1980s

45
1990s

46
2000s

44
2010s

19
2020s

14

What this shows Construction peaked in the 1970s, when 52 of the county's bridges still in the inventory were built, which is 17.8% 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 Canyon County compares with Idaho's closest counties by inventory size

The 5 Idaho counties nearest Canyon County in number of bridges, with their condition splits. Its 2.7% Poor share is the 2nd-lowest of these 6. Its average build year of 1984 against a peer-group mean of 1977 is 7 years newer.

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

Bridge inventory size and condition shares for Canyon County and the 5 Idaho counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Ada County	299	41.8%	58.2%	0%	1989
Canyon County (this page)	292	27.7%	69.5%	2.7%	1984
Bingham County	263	17.1%	79.5%	3.4%	1975
Shoshone County	260	21.5%	68.8%	9.6%	1971
Idaho County	215	37.2%	56.7%	6%	1975
Bonneville County	213	30.5%	66.7%	2.8%	1977

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

Similar inventory size

Nearest county inventories outside ID (292 bridges here).

Hancock County, IL · 292 bridges
Logan County, IL · 292 bridges
Jackson County, OK · 292 bridges
Clearfield County, PA · 292 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 292 Good 81 Fair 203 Poor 8

Good-condition bridges (81)

Sort:

Canyon County Bridge Snapshot

Condition distribution

Canyon County's Poor-condition bridges carry 33,990 vehicle crossings a day

34.9% of Canyon County's bridges have passed the 50-year mark

One structure carries 58.8% of the county's Poor-condition bridge traffic

How Canyon 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

Good-condition bridges (81)

STC 8223;KARCHER R

SH 55

I 84 WBL & EBL

STP 7933;21ST AVE

STC 7819;KINGS RD

MOSS LANE

STC3753;LONE STAR

JOHNSON LANE

SH 55

NHS 7983;USTICK RD

STC3756;DEER FLAT

LEWIS LANE

I 84 EBL WBL

STC 3874;STAFFORD

STP7933;FRANKLIN R

STC7158;COMMERCIAL

MORENO DRIVE

STC8533;SMITH AVE

STC3866;BOISE R RD

I 84 OFF RAMP

US 95

MARSING ROAD

STC3725;LAKE SHORE

SMA8133;HWY 44 EXT

STC3756;DEER FLAT

RIM ROAD

US 20

LINDEN ROAD

LAKE SHORE

STC3742;WAMSTAD RD

SH 55

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