County profile · official public datasets

Iroquois County, IL

570 public highway bridges tracked in the FHWA National Bridge Inventory: 46.5% rated Good, 39.1% Fair, 14.4% Poor.

570
Public bridges
46.5%
Good condition
14.4%
Poor condition

The verdict

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

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

90th
of 102 on Poor share
14.4%
Poor-condition share
570
public highway bridges
1980
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.

Iroquois County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Iroquois County ranks #90 of 102 Illinois counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 14.4%). Iroquois County, Illinois contains 570 public highway bridges. Roughly 46.5% are rated “Good,” 39.1% “Fair,” and 14.4% “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

570

Public highway bridges in Iroquois County

Good condition

46.5%

265 of 570 rated 7-9

Fair condition

39.1%

223 of 570 rated 5-6

Poor condition

14.4%

82 of 570 rated 4 or below

In-state Poor-share rank

#90 of 102

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

Condition distribution

Share of 570 NBI-tracked bridges by lowest applicable component rating.

Good
46.5% (265)
Fair
39.1% (223)
Poor
14.4% (82)

Iroquois County's Poor-condition bridges carry 75,495 vehicle crossings a day

That is 16.1% of the county's reported daily bridge traffic on 14.4% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 921 crossings a day against 395 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 569 of 570 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

34.2% of Iroquois County's bridges have passed the 50-year mark

195 of the 570 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 46.5% 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 12% of the county's Poor-condition bridge traffic

FAI-57 NB over IC RR, built 1967, carries 9,050 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 82-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 75,495 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

When Iroquois County's bridges were built

570 bridges with a recorded construction year, grouped by decade

bridges

What this shows Construction peaked in the 1980s, when 115 of the county's bridges still in the inventory were built, which is 20.2% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year (1980) matches the Illinois average (1979).

Source FHWA National Bridge Inventory (year built) As of 2024 NBI release

How Iroquois County compares with Illinois's closest counties by inventory size

The 5 Illinois counties nearest Iroquois County in number of bridges, with their condition splits. Its 14.4% Poor share is the 6th-lowest of these 6. Its average build year of 1980 against a peer-group mean of 1979 is in line with the group.

Showing the 5 closest of 101 Illinois counties eligible for comparison.

Bridge inventory size and condition shares for Iroquois County and the 5 Illinois counties closest to it in inventory size
County Bridges Poor
McLean County 624 2.9%
Livingston County 579 8.3%
Iroquois County (this page) 570 14.4%
LaSalle County 528 12.3%
Madison County 523 8.4%
Vermilion County 494 7.3%

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

Similar inventory size

Nearest county inventories outside IL (570 bridges here).

Similar average build year

Nearest mean year-built outside IL (1980 here).

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

All 570 Good 265 Fair 223 Poor 82

Good-condition bridges (265)

TR 434

Good

Over: TRIB TO SUGAR CREEK

1.2 MI E OF CH41, Iroquois, IL

Built 1999 Load: 32.4 t ADT: 50

TR 251

Good

Over: COON CR

2.7M S 5M E WOODLAND, Iroquois, IL

Built 2008 Load: 32.4 t ADT: 75

TR 434

Good

Over: MUD CREEK

2M E 1M N STOCKLAND, Iroquois, IL

Built 2008 Load: 32.4 t ADT: 50

WEST ST MS6000 CIS

Good

Over: TRIB.TO PIGEON CREEK

SW EDGE OF CISSNA PK, Iroquois, IL

Built 2003 Load: 32.4 t ADT: 75

CITY ST.#6100

Good

Over: MCCUTCHEON DITCH

CRESCENT CITY, Iroquois, IL

Built 1983 Load: 32.4 t ADT: 125

FAS 323 CH 40

Good

Over: COON CR

2.19 MI W OF IL 1, Iroquois, IL

Built 1991 Load: 33.4 t ADT: 650

TR 331A

Good

Over: DITCH

3.7 MI E OF ILL 1, Iroquois, IL

Built 2021 Load: 33.7 t ADT: 75

TR 22C

Good

Over: TRIB SPRING CR

1MI S ILL 54, Iroquois, IL

Built 1976 Load: 34.3 t ADT: 50

US 52

Good

Over: MARTINTON DITCH NO 3

2.55 MI E OF IL 1, Iroquois, IL

Built 2015 Load: 35.0 t ADT: 1,700

TR 188

Good

Over: PRAIRIE CR

2 MI E LERABLE, Iroquois, IL

Built 1975 Load: 35.0 t ADT: 50

CH 4 OVER PIKE CR

Good

Over: PIKE CREEK

3.25 MI W SBI 1, Iroquois, IL

Built 2022 Load: 35.0 t ADT: 425

FAS 326 BRYCE RD

Good

Over: JEFFERSON CREEK

1.04 MI S OF FAS 323, Iroquois, IL

Built 1988 Load: 35.3 t ADT: 475

US 24

Good

Over: DRAINAGE DITCH

.05 MILE E OF ILL 49, Iroquois, IL

Built 1994 Load: 35.3 t ADT: 4,500

FAS 329 CH-10

Good

Over: TRIB. PIGEON CR

1.39 MI E OF ILL 49, Iroquois, IL

Built 1985 Load: 35.3 t ADT: 500

IL 49 FAP 840

Good

Over: Drainage Ditch

0.48 Mi N of US 24, Iroquois, IL

Built 2015 Load: 36.0 t ADT: 2,300

TR 371A

Good

Over: TRIB TO GAY CREEK

0.5 MI W RTE 1, Iroquois, IL

Built 1983 Load: 36.0 t ADT: 50

TWP RD 327

Good

Over: FAI 57

1.07 MI S BUCKLEY IN, Iroquois, IL

Built 1968 Load: 36.3 t ADT: 100

US 45-52/FAP 840

Good

Over: Drainage Ditch

0.30 mi S of K3 Co, Iroquois, IL

Built 2013 Load: 36.3 t ADT: 3,650

TR 353

Good

Over: PIGEON CREEK

SEC 7 T24N R13W 2ND, Iroquois, IL

Built 1996 Load: 36.3 t ADT: 25

FAS327-CH41

Good

Over: POSSUM TROT DITCH

3.8MI S US24, Iroquois, IL

Built 1994 Load: 36.3 t ADT: 325

CH 4

Good

Over: BRANCH OF LANGAN CRK

6 MI E. OF FORD CO., Iroquois, IL

Built 1992 Load: 36.9 t ADT: 150

TR 159B (WAS OR 7)

Good

Over: DRAINAGE DITCH

0.81 MI NWOF US 24, Iroquois, IL

Built 1986 Load: 36.9 t ADT: 275

TR 44

Good

Over: PRAIRE CREEK

2.25MI NW GILMAN, Iroquois, IL

Built 1954 Load: 37.3 t ADT: 75

FAS 329/CH 10

Good

Over: WHISKY CREEK

2.95 MI E.OF IL 49, Iroquois, IL

Built 1999 Load: 37.3 t ADT: 500

TR 286

Good

Over: LITTLE BEAVER CREEK

1.75 mi S of St.Anne, Iroquois, IL

Built 2020 Load: 37.3 t ADT: 275

FAS 334 (CH 9)

Good

Over: TRIB. TO LOUIS CREEK

0.5 MI W BUCKLEY, Iroquois, IL

Built 2001 Load: 37.6 t ADT: 1,050

TR 353

Good

Over: FOUNTAIN CR

1 MI E OF CH 6, Iroquois, IL

Built 1994 Load: 37.6 t ADT: 25

FAS 1324/OLD US 45

Good

Over: TRIB OF LANGAN CREEK

1.2 MI S OF CHEBANSE, Iroquois, IL

Built 1987 Load: 37.9 t ADT: 1,900

FAS 323 ONARGA RD

Good

Over: SPRING CREEK

5.62 MI W OF ILL 49, Iroquois, IL

Built 1989 Load: 37.9 t ADT: 450

TR 251

Good

Over: SUGAR CREEK

2 MI S OF WOODLAND, Iroquois, IL

Built 1987 Load: 37.9 t ADT: 200

FAS 1322 CH37

Good

Over: TR1 B OF TRAIL CR

0.34 MI E US 52, Iroquois, IL

Built 1932 Load: 38.2 t ADT: 575

US 52

Good

Over: DRAINAGE DITCH

0.43 M N US 24, Iroquois, IL

Built 1994 Load: 38.2 t ADT: 1,200

IL 116 (FAP 681)

Good

Over: drainage ditch

2.15 MI W of I-57, Iroquois, IL

Built 2016 Load: 38.2 t ADT: 850

CH 15

Good

Over: Pike Creek

2 mi. S. of Donovan, Iroquois, IL

Built 2014 Load: 38.2 t ADT: 150

ILL 49

Good

Over: BR SHAVETAIL CRK

5.51 MI S JCT 49&24, Iroquois, IL

Built 1996 Load: 38.6 t ADT: 1,000

TR 9A

Good

Over: LITTLE BEAVER CREEK

1.5N 0.5W PAPINEAU, Iroquois, IL

Built 1985 Load: 38.6 t ADT: 100

US 45

Good

Over: LOUIS CREEK

1.68 MI N OF BUCKLEY, Iroquois, IL

Built 2007 Load: 39.2 t ADT: 1,050

US 45

Good

Over: DRAINAGE DITCH

0.39 MI S OF US 24, Iroquois, IL

Built 2004 Load: 39.5 t ADT: 3,000

US 45

Good

Over: Prairie Creek

2.35 M N of US 24, Iroquois, IL

Built 2020 Load: 40.5 t ADT: 1,350

TR 51

Good

Over: BEAVER DITCH NO. 1

5.3 MI E MARTINTON, Iroquois, IL

Built 2023 Load: 40.8 t ADT: 75

TR 5

Good

Over: DRAINAGE DITCH

4.75 W 3.5 N CLIFTON, Iroquois, IL

Built 1987 Load: 40.8 t ADT: 50

TR 68

Good

Over: PRAIRIE CR

3.2MI N GILMAN, Iroquois, IL

Built 1972 Load: 41.1 t ADT: 50

Stockland Road

Good

Over: SUGAR CREEK

9.66 M S OF US 24, Iroquois, IL

Built 1994 Load: 42.8 t ADT: 300

IL 1

Good

Over: Pike Creek

0.15 M N of US 52, Iroquois, IL

Built 2021 Load: 42.8 t ADT: 2,250

US 45/52

Good

Over: Trib to Langan Creek

3.51 M N of US 52, Iroquois, IL

Built 2019 Load: 43.1 t ADT: 3,650

IL 116

Good

Over: LANGAN CREEK

3.97M E FORD C LN, Iroquois, IL

Built 1992 Load: 43.4 t ADT: 850

DANFORTH RD

Good

Over: PRAIRIE CREEK

3.74 M W OF IL 49, Iroquois, IL

Built 1994 Load: 44.1 t ADT: 250

IL 1

Good

Over: Gay Creek

0.16M S ofWellington, Iroquois, IL

Built 2022 Load: 44.4 t ADT: 2,200

TR 2 D

Good

Over: Sheldon Ditch #1

0.9 Mi S of CR1400S, Iroquois, IL

Built 1900 Load: 44.4 t ADT: 75

IL 1

Good

Over: IROQUOIS RIVER

1.0 MI N of US 24, Iroquois, IL

Built 2015 Load: 45.7 t ADT: 2,600

Read our methodology - how this data is sourced, computed, and verified.

Related

Browse all → | Rankings →
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges

Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.