County profile · official public datasets

Grundy County, IL

269 public highway bridges tracked in the FHWA National Bridge Inventory: 40.5% rated Good, 32.7% Fair, 26.8% Poor.

269
Public bridges: 40.5%
Good condition: 26.8%
Poor condition

The verdict

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

Grundy 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.

102nd
of 102 on Poor share: 26.8%
Poor-condition share: 269
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.

Grundy County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Grundy County ranks #102 of 102 Illinois counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 26.8%). Grundy County, Illinois contains 269 public highway bridges. Roughly 40.5% are rated “Good,” 32.7% “Fair,” and 26.8% “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

269

Public highway bridges in Grundy County

Good condition

40.5%

109 of 269 rated 7-9

Fair condition

32.7%

88 of 269 rated 5-6

Poor condition

26.8%

72 of 269 rated 4 or below

In-state Poor-share rank

#102 of 102

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

Condition distribution

Share of 269 NBI-tracked bridges by lowest applicable component rating.

Good

40.5% (109)

Fair

32.7% (88)

Poor

26.8% (72)

Grundy County's Poor-condition bridges carry 88,350 vehicle crossings a day

That is 13.6% of the county's reported daily bridge traffic on 26.9% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 1,227 crossings a day against 2,660 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 268 of 269 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

20.4% of Grundy County's bridges have passed the 50-year mark

55 of the 269 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 40.5% 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 23.8% of the county's Poor-condition bridge traffic

ILL 47 over ARMSTRONG & B & O RR, built 1978, carries 21,000 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 72-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 88,350 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

6
1930s

5
1940s

2
1950s

19
1960s

15
1970s

50
1980s

70
1990s

38
2000s

37
2010s

24
2020s

3

What this shows Construction peaked in the 1980s, when 70 of the county's bridges still in the inventory were built, which is 26% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year is 1984, 5 years newer than the Illinois average of 1979.

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

The 5 Illinois counties nearest Grundy County in number of bridges, with their condition splits. Its 26.8% Poor share is the 6th-lowest of these 6. Its average build year of 1984 against a peer-group mean of 1980 is in line with the group.

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

Bridge inventory size and condition shares for Grundy County and the 5 Illinois counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Edgar County	278	50.7%	45.3%	4%	1977
Rock Island County	272	46%	49.3%	4.8%	1983
Grundy County (this page)	269	40.5%	32.7%	26.8%	1984
Wayne County	266	54.1%	36.8%	9%	1982
DeKalb County	261	40.6%	46.4%	13%	1981
Montgomery County	261	52.1%	40.6%	7.3%	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 Grundy 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 Grundy County, both outside Illinois so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside IL (269 bridges here).

Bartholomew County, IN · 269 bridges
Rensselaer County, NY · 269 bridges
Harrison County, TX · 269 bridges
Manitowoc County, WI · 269 bridges

Similar average build year

Nearest mean year-built outside IL (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 269 Good 109 Fair 88 Poor 72

All bridges (269)

Sort:

Grundy County Bridge Snapshot

Condition distribution

Grundy County's Poor-condition bridges carry 88,350 vehicle crossings a day

20.4% of Grundy County's bridges have passed the 50-year mark

One structure carries 23.8% of the county's Poor-condition bridge traffic

How Grundy County compares with Illinois'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 (269)

TR-58 BUFFALO RD

TR 3B MINOOKA ROAD

CAMPUS ROAD

CAMPUS ROAD

TYNAN ROAD CH C41

TR-103 OMALLEY RD

TR 107 WAUPECAN RD

OMALLEY RD TR-103

Saratoga Rd / TR 8

Pioneer Rd / TR 78

RICE RD CH 15

OLD STAGE RD CH 28

LA SALLE RD TR-2

GOULD ST

TR-110

GARDNER Rd/FAS 292

JOHNNY RUN ROAD

SWELL RD TR 40

TR-49 (STOCKDALE R

TR120 OLDMAZON RD

GOODFARM RD

TR 78

TR-3B MINOOKA RD

TR 71 SHABBONA RD

TR 89A/Indian Trai

MCARDLE RD-TR91A

TR 180A Walleye Ro

TR 91A MCARDLE RD

TR 20 JOHNNY RUN R

TR 1E LIV.CO.

TR 72 VERONA RD

DWIGHT RD TR-110

HOWLAND RD/MS 2020

CREEK DR./MS 1115

MINOOKA RD/FAU400

TR 123 PRAIRIE ROA

TR 130 HIGGINS RD

TR-74A Verona Road

TR 159A STONEWALL

FAS 1273/DuPont Rd

TR-128 TYNAN RD

GONNAM RD TR-32

GRINTER RD TR-129

VERONA RD TR-74A

US 6

TR 25A CEMETERY RD

FAS-288 (CH-18)

BENNETT RD TR-22

TR 155

TR-13 HOGE RD

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