County profile · official public datasets

Winnebago County, IL

467 public highway bridges tracked in the FHWA National Bridge Inventory: 31.3% rated Good, 61.7% Fair, 7.1% Poor.

467
Public bridges
31.3%
Good condition
7.1%
Poor condition

The verdict

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

Winnebago County posts a better-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.

Top 42%
lowest Poor share in state
7.1%
Poor-condition share
467
public highway bridges
1978
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.

Winnebago County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Winnebago County ranks #43 of 102 Illinois counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 7.1%). Winnebago County, Illinois contains 467 public highway bridges. Roughly 31.3% are rated “Good,” 61.7% “Fair,” and 7.1% “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

467

Public highway bridges in Winnebago County

Good condition

31.3%

146 of 467 rated 7-9

Fair condition

61.7%

288 of 467 rated 5-6

Poor condition

7.1%

33 of 467 rated 4 or below

In-state Poor-share rank

#43 of 102

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

Condition distribution

Share of 467 NBI-tracked bridges by lowest applicable component rating.

Good
31.3% (146)
Fair
61.7% (288)
Poor
7.1% (33)

Winnebago County's Poor-condition bridges carry 180,060 vehicle crossings a day

That is 4.9% of the county's reported daily bridge traffic on 7.1% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 5,456 crossings a day against 6,482 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 467 of 467 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

49.5% of Winnebago County's bridges have passed the 50-year mark

231 of the 467 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 31.3% 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 14.1% of the county's Poor-condition bridge traffic

I-39 SB over HARRISON AVE, built 1963, carries 25,450 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 33-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 180,060 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

When Winnebago County's bridges were built

467 bridges with a recorded construction year, grouped by decade

bridges

What this shows Construction peaked in the 1960s, when 121 of the county's bridges still in the inventory were built, which is 25.9% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1978) matches the Illinois average (1979).

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

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

The 5 Illinois counties nearest Winnebago County in number of bridges, with their condition splits. Its 7.1% Poor share is the 2nd-lowest of these 6. Its average build year of 1978 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 Winnebago County and the 5 Illinois counties closest to it in inventory size
County Bridges Poor
LaSalle County 528 12.3%
Madison County 523 8.4%
Vermilion County 494 7.3%
St. Clair County 486 9.1%
Winnebago County (this page) 467 7.1%
Sangamon County 466 6.2%

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

Similar inventory size

Nearest county inventories outside IL (467 bridges here).

Similar average build year

Nearest mean year-built outside IL (1978 here).

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

All 467 Good 146 Fair 288 Poor 33

Poor-condition bridges (33)

ROSCOE RD

Poor

Over: ROCK RIVER

0.2 MI. W. IL 251, Winnebago, IL

Built 1967 Load: 0.0 t ADT: 10,700

8TH AV

Poor

Over: KEITH CREEK

0.05 MI E KISHWAUKEE, Winnebago, IL

Built 1919 Load: 5.5 t ADT: 375

ELM STREET-ROCKFOR

Poor

Over: KENT CREEK

0.5 MI W OF DOWNTOWN, Winnebago, IL

Built 1992 Load: 10.4 t ADT: 35

KILBUCK BLUFF FP

Poor

Over: BR KILBUCK CR

BY KILBUCK CREEK, Winnebago, IL

Built 1926 Load: 14.3 t ADT: 475

GOEKE ROAD

Poor

Over: PINK CREEK

100FT N BRICK SCH RD, Winnebago, IL

Built 1999 Load: 16.8 t ADT: 75

GLEASMAN ROAD

Poor

Over: UNNAMED CREEK

0.2 MI E ROCKTON AVE, Winnebago, IL

Built 1935 Load: 17.5 t ADT: 800

GUILFORD ROAD

Poor

Over: KEITH CR

0.7 MI E OF ALPINE R, Winnebago, IL

Built 1952 Load: 19.4 t ADT: 10,150

LIBERTY DR

Poor

Over: NW DRAINAGEWAY

0.35 MI W OF KILBURN, Winnebago, IL

Built 1962 Load: 19.4 t ADT: 1,400

GILBERT AVE

Poor

Over: NW DRAINAGEWAY

0.25 MI W OF KILBURN, Winnebago, IL

Built 1962 Load: 22.7 t ADT: 1,150

CORBIN ST

Poor

Over: KENT CREEK

0.15 MI N CUNNINGHAM, Winnebago, IL

Built 1937 Load: 24.0 t ADT: 950

MERIDIAN RD

Poor

Over: PECATONICARIVER

0.7 MI SE SHIRLAND, Winnebago, IL

Built 1973 Load: 26.2 t ADT: 1,650

HAMBORG ROAD

Poor

Over: STONEBRIDGE TRAIL

0.25 M E OF I-90, Winnebago, IL

Built 1981 Load: 26.6 t ADT: 1,100

N 3RD ST EXT TO 2N

Poor

Over: SB RAMP TO N 6TH ST

WHITMAN INTERCHANGE, Winnebago, IL

Built 1963 Load: 26.6 t ADT: 8,200

LATHAM-RALSTON RD

Poor

Over: ROCK RIVER

1 MI. E. ILL 2, Winnebago, IL

Built 1969 Load: 26.9 t ADT: 8,200

SIMPSON ROAD

Poor

Over: FULLERS CR

0.2 MI E PRAIRIE RD, Winnebago, IL

Built 1959 Load: 27.2 t ADT: 700

SAUNDERS RD

Poor

Over: UNNAMED CREEK

3.5 MI E OF PECATONI, Winnebago, IL

Built 1957 Load: 28.8 t ADT: 800

I-39 NB

Poor

Over: HARRISON AVE

.6 MI S OF I-90, Winnebago, IL

Built 1963 Load: 29.8 t ADT: 21,150

CENTERVILLE ROAD

Poor

Over: SO FORK KENT CREEK

0.1 MI S CUNNINGHAM, Winnebago, IL

Built 1928 Load: 30.5 t ADT: 400

CUNNINGHAM RD

Poor

Over: CN RR

0.5 MI E PIERPONT, Winnebago, IL

Built 1955 Load: 31.4 t ADT: 2,650

11TH STREET

Poor

Over: KEITH CREEK

0.52 N BROADWAY, Winnebago, IL

Built 1915 Load: 32.4 t ADT: 9,300

MERIDIAN RD

Poor

Over: CN RR

0.5 MI S CUNNINGHAM, Winnebago, IL

Built 1954 Load: 33.4 t ADT: 2,450

PRAIRIE HILL RD

Poor

Over: ROCK RIVER

0.4 MI W ILL 2, Winnebago, IL

Built 1966 Load: 34.3 t ADT: 4,200

ILL 70

Poor

Over: TRIB. OF PECATONICA

.5 MI W CEMETERY RD, Winnebago, IL

Built 1982 Load: 35.0 t ADT: 3,500

WINNEBAGO STREET

Poor

Over: KENT CR & RR TRACKS

0.4 MI S OF STATE ST, Winnebago, IL

Built 1982 Load: 36.3 t ADT: 4,900

SPRINGFIELD AVE

Poor

Over: N FORK KENT CREEK

0.5 MI S OF ILL 70, Winnebago, IL

Built 1959 Load: 36.6 t ADT: 8,500

ILL 251 S B

Poor

Over: UP RR

2.5 MI SOUTH ILL 75, Winnebago, IL

Built 1967 Load: 36.9 t ADT: 13,000

ILL 251 N B

Poor

Over: UP RR

2.5 MI S ILL 75, Winnebago, IL

Built 1967 Load: 36.9 t ADT: 13,000

15TH AVE

Poor

Over: ROCK RIVER

0.01 M E OF MAIN, Winnebago, IL

Built 1980 Load: 37.3 t ADT: 5,750

IL 70

Poor

Over: TRIB. OF PECATONICA

.6 MI W CEMETERY RD, Winnebago, IL

Built 1982 Load: 38.9 t ADT: 3,500

ILL 70

Poor

Over: TRIB. OF PECATONICA

.1 MI W CEMETERY RD, Winnebago, IL

Built 1982 Load: 38.9 t ADT: 2,950

JONATHAN AVE

Poor

Over: NW DRAINAGEWAY

0.1 MI E OF ROCKTON, Winnebago, IL

Built 1962 Load: 44.4 t ADT: 200

AUBURN ST.

Poor

Over: KENT CREEK

0.1 MI W OF KILBURN, Winnebago, IL

Built 1930 Load: 47.6 t ADT: 12,400

I-39 SB

Poor

Over: HARRISON AVE

.6 MI S OF I-90, Winnebago, IL

Built 1963 Load: 55.4 t ADT: 25,450

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.