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.

When Grundy County's bridges were built

269 bridges with a recorded construction year, grouped by decade

bridges

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.

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

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 Poor
Edgar County 278 4%
Rock Island County 272 4.8%
Grundy County (this page) 269 26.8%
Wayne County 266 9%
DeKalb County 261 13%
Montgomery County 261 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 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).

Similar average build year

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

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

Fair-condition bridges (88)

FAS-292 Gardner Rd

Fair

Over: Murray Sluice

.28 MI W WARD TR84, Grundy, IL

Built 2002 Load: 36.9 t ADT: 850

TR 56

Fair

Over: THUNDER CREEK

300 S PRAIRIE RD, Grundy, IL

Built 2008 Load: 36.9 t ADT: 25

CH 32 GARDNER RD

Fair

Over: TRIB TO WAPECON CR

.01 MI E LASALLE RD, Grundy, IL

Built 1988 Load: 37.3 t ADT: 900

ILL 53 FAP 846

Fair

Over: MAZON RIVER

1.3 M N OF GARDNER, Grundy, IL

Built 1969 Load: 37.6 t ADT: 1,400

GORMAN RD CH 10

Fair

Over: MAZON RIVER

0.04 MI N TR 109B, Grundy, IL

Built 1987 Load: 37.9 t ADT: 300

FAS 292/GARDNER RD

Fair

Over: I 55

GARD. RD INTERCHANGE, Grundy, IL

Built 1997 Load: 38.6 t ADT: 2,400

IL 47 FAP 326

Fair

Over: IL RIV.& I & M CANAL

APPR.1.23MI S /US 6, Grundy, IL

Built 2003 Load: 38.9 t ADT: 18,100

TR 74

Fair

Over: TRIB.OF WAUPECON CRK

W4000 S1400, Grundy, IL

Built 1998 Load: 38.9 t ADT: 325

TR 182

Fair

Over: FAI 55

4.79 MI S OF REED RD, Grundy, IL

Built 1993 Load: 39.9 t ADT: 1,550

FAI 80 EBL

Fair

Over: W FORK NETTLE CR

2.52 MI W OF IL 47, Grundy, IL

Built 1958 Load: 40.2 t ADT: 15,300

FAI 80 WBL

Fair

Over: W FORK NETTLE CR

2.52 MI W OF IL 47, Grundy, IL

Built 1958 Load: 40.2 t ADT: 15,300

TR-167 SCULLY RD

Fair

Over: TRIB E FK MAZON RIV

.09 MI W CH-31, Grundy, IL

Built 2005 Load: 40.2 t ADT: 50

ILL 47

Fair

Over: MURRAY CREEK

7.23 MILES N OF I-55, Grundy, IL

Built 1994 Load: 40.5 t ADT: 4,550

MINOOKA RD TR 3

Fair

Over: TRIB W FR NETTLE CR

0.57MI E. ROODS RD, Grundy, IL

Built 1991 Load: 40.8 t ADT: 175

FAI 080 (EB & WB)

Fair

Over: AUX SABLE CRK

7.73 MI E OF ILL 47, Grundy, IL

Built 2003 Load: 41.1 t ADT: 39,100

FAI 80 WBL

Fair

Over: E FORK NETTLE CR

1.3 MI W OF ILL 47, Grundy, IL

Built 1958 Load: 42.1 t ADT: 15,300

T.R. 103 /OMalley

Fair

Over: HOG RUN

0.1 mi. E.Kingman Rd, Grundy, IL

Built 2016 Load: 42.4 t ADT: 175

TR-105 (Spring Rd)

Fair

Over: MAZON RIVER

.3 MI E CAMPBELL RD, Grundy, IL

Built 1910 Load: 42.8 t ADT: 100

REED ROAD TR-107B

Fair

Over: MAZON RIVER

.33 MI W GORMAN RD, Grundy, IL

Built 1981 Load: 43.4 t ADT: 275

ILL 47

Fair

Over: BREWSTER RUN

N OF I-55, Grundy, IL

Built 2004 Load: 44.7 t ADT: 3,600

WABENA ST-MINOOKA

Fair

Over: FAI 80

0.5 M E MINOOKA INT, Grundy, IL

Built 1959 Load: 45.4 t

IL 47 FAP 326

Fair

Over: W FORK MAZON RIVER

6.1 MI N OF I-55, Grundy, IL

Built 2009 Load: 46.0 t ADT: 4,550

FAP 623 (AT OR 623

Fair

Over: I-80 EB & WB

SENECA JUNCTION, Grundy, IL

Built 2006 Load: 47.0 t ADT: 3,050

I-80EB Entrance Ra

Fair

Over: COLLINS RUN

SE QUAD I-80/BRISBIN, Grundy, IL

Built 2011 Load: 47.3 t ADT: 1,050

NETTLE CR ROAD CH-

Fair

Over: WEST FORK NETTLE CR

0.1 MI N OF TR 13, Grundy, IL

Built 1964 Load: 48.0 t ADT: 100

BRISBIN RD (FAU 40

Fair

Over: FAI 80

3.72 MI E OF ILL 47, Grundy, IL

Built 2011 Load: 48.6 t ADT: 1,825

ILL 113

Fair

Over: MAZON RIVER

3.12 M E. OF ILL 47, Grundy, IL

Built 2000 Load: 49.6 t ADT: 4,450

IL 47 FAP 326

Fair

Over: JOHNNY RUN

S EDGE OF MAZON, Grundy, IL

Built 2009 Load: 50.5 t ADT: 4,550

MINOOKA RD / CH 16

Fair

Over: I-80

2.56 M W Minooka Int, Grundy, IL

Built 2015 Load: 51.2 t ADT: 1,500

FAI 80 (EB & WB)

Fair

Over: FAS285/CH5/RIDGE RD

MINOOKA INTERCHANGE, Grundy, IL

Built 2003 Load: 51.8 t ADT: 50,300

FAI 55 NB

Fair

Over: Union Pacific RR

3.2 MI S OF REED RD, Grundy, IL

Built 1955 Load: 52.2 t ADT: 12,050

FAI 55 SB

Fair

Over: Union Pacific RR

3.2 MI S OF REED RD, Grundy, IL

Built 1955 Load: 52.2 t ADT: 12,050

MARSEILLES RD CH 2

Fair

Over: LONG POINT CREEK

0.37 MI W OF US 6, Grundy, IL

Built 2004 Load: 52.2 t ADT: 2,050

ILL 113/FAS 301

Fair

Over: BR OF MAZON RIVER

2.75 M. E. OF IL 47, Grundy, IL

Built 2003 Load: 53.5 t ADT: 4,450

FAI 55 NB

Fair

Over: MAZON RIVER @ TR 125

4.1 MI S OF REED RD, Grundy, IL

Built 1955 Load: 55.1 t ADT: 12,050

FAI 55 SB

Fair

Over: MAZON RIVER @ TR 125

4.1 MI S OF REED RD, Grundy, IL

Built 1955 Load: 55.1 t ADT: 12,050

PINE BLUFF RD CH-2

Fair

Over: MAZON RIVER

0.12 MI W OF TR 45, Grundy, IL

Built 2010 Load: 58.6 t ADT: 4,600

TR 119 BOOTH ROAD

Fair

Over: TRIB E FK MAZON RIV

.27 MI E TYNAN ROAD, Grundy, IL

Built 1981 Load: 68.7 t ADT: 50

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

Related

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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.