Total bridges
269
Public highway bridges in Grundy County
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.
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
- 1910s 6
1910–1919
6 bridges
- 1930s 5
1930–1939
5 bridges
- 1940s 2
1940–1949
2 bridges
- 1950s 19
1950–1959
19 bridges
- 1960s 15
1960–1969
15 bridges
- 1970s
1970–1979
50 bridges
- 1980s
1980–1989
70 bridges
- 1990s
1990–1999
38 bridges
- 2000s
2000–2009
37 bridges
- 2010s 24
2010–2019
24 bridges
- 2020s 3
2020–2029
3 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.
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.
| 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 bridges (269)
TR-14 Nettle Crk R
PoorOver: Trib To Nettle Crk
0.21 MI S OF TR 13, Grundy, IL
Built 1977 Load: 31.8 t ADT: 100
TR70 SCOTTSCHOOL R
PoorOver: WEST FORK NETTLE CR
.18 MI S HOGE RD, Grundy, IL
Built 1981 Load: 32.1 t ADT: 225
TR 172 JUGTOWN RD
PoorOver: CLAYPOOL DRAIN DITCH
.11 MI S WHITETIE RD, Grundy, IL
Built 1986 Load: 32.1 t ADT: 900
HIGGINS RD TR-130
PoorOver: JOHNNY RUN
.41 MI N SPRING RD, Grundy, IL
Built 1977 Load: 32.1 t ADT: 125
TR 106 ASHTON RD
PoorOver: E FK NETTLE CREEK
0.08 MI S NELSON RD, Grundy, IL
Built 1986 Load: 32.4 t ADT: 225
TR-110 DWIGHT RD
PoorOver: JOHNNY RUN
.08 MI N MINE RD, Grundy, IL
Built 1981 Load: 32.4 t ADT: 150
GARDNER RD/FAS 292
PoorOver: JOHNNY RUN
.36 MI W-BUFFALO RD, Grundy, IL
Built 1992 Load: 32.4 t ADT: 800
GOODFARM RD TR-155
PoorOver: TRIB E FK MAZON RIV
.13 MI E HALPIN RD, Grundy, IL
Built 1980 Load: 32.4 t ADT: 50
TR 161 STONEWALL R
PoorOver: TRIB E FK MAZON R
.06 MI W KANKAKEE RD, Grundy, IL
Built 1988 Load: 32.4 t ADT: 75
TR 155/GOODFARM RD
PoorOver: E FORK MAZON RIVER
1 S SOUTH WILMINGTON, Grundy, IL
Built 1999 Load: 33.4 t ADT: 50
ARMSTRONG STREET
PoorOver: I&M CANAL
150 E OF WASHINGTON, Grundy, IL
Built 1990 Load: 34.0 t ADT: 900
US 6
PoorOver: AUX SABLE CR
4.9 M E OF ILL 47, Grundy, IL
Built 1969 Load: 35.0 t ADT: 7,050
FAS-292 Gardner Ro
PoorOver: W Fork Mazon River
0.05M E Dwight Road, Grundy, IL
Built 1982 Load: 35.0 t ADT: 1,000
HOGE RD TR-13
PoorOver: TRIB TO NETTLE CREEK
0.06 MI E OF CH 21, Grundy, IL
Built 1976 Load: 37.3 t ADT: 25
ILL 47
PoorOver: BUCHANAN ST
ILL 47 IN MORRIS, Grundy, IL
Built 1978 Load: 37.9 t ADT: 21,000
TR 2 LA SALLE RD
PoorOver: TRIB TO JOHNNY RUN
.15 MI S SCULLY RD, Grundy, IL
Built 1985 Load: 37.9 t ADT: 25
KINSMAN ROAD
PoorOver: WAUPECON CREEK
0.1 MI N BURKHART RD, Grundy, IL
Built 1948 Load: 39.2 t ADT: 300
ILL 47
PoorOver: ARMSTRONG & B & O RR
.57 S OF US 6 WEST, Grundy, IL
Built 1978 Load: 39.9 t ADT: 21,000
Brown Rd / TR 150
PoorOver: FAI 80
4.48 MI E OF ILL 47, Grundy, IL
Built 1960 Load: 54.1 t ADT: 350
Read our methodology - how this data is sourced, computed, and verified.
Related
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.