County profile · official public datasets

Knox County, IL

304 public highway bridges tracked in the FHWA National Bridge Inventory: 49.3% rated Good, 39.5% Fair, 11.2% Poor.

304
Public bridges
49.3%
Good condition
11.2%
Poor condition

The verdict

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

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

80th
of 102 on Poor share
11.2%
Poor-condition share
304
public highway bridges
1982
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.

Knox County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Knox County ranks #80 of 102 Illinois counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 11.2%). Knox County, Illinois contains 304 public highway bridges. Roughly 49.3% are rated “Good,” 39.5% “Fair,” and 11.2% “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

304

Public highway bridges in Knox County

Good condition

49.3%

150 of 304 rated 7-9

Fair condition

39.5%

120 of 304 rated 5-6

Poor condition

11.2%

34 of 304 rated 4 or below

In-state Poor-share rank

#80 of 102

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

Condition distribution

Share of 304 NBI-tracked bridges by lowest applicable component rating.

Good
49.3% (150)
Fair
39.5% (120)
Poor
11.2% (34)

Knox County's Poor-condition bridges carry 55,695 vehicle crossings a day

That is 13.5% of the county's reported daily bridge traffic on 11.2% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 1,638 crossings a day against 609 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 303 of 304 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

31.3% of Knox County's bridges have passed the 50-year mark

95 of the 304 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 49.3% 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 13.8% of the county's Poor-condition bridge traffic

WB I-74 over SPOON R & TR 238A, built 1968, carries 7,700 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 34-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 55,695 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

When Knox County's bridges were built

304 bridges with a recorded construction year, grouped by decade

bridges

What this shows Construction peaked in the 1990s, when 56 of the county's bridges still in the inventory were built, which is 18.4% of those with a recorded year. That cohort is now 25 to 34 years old in the 2024 inventory. Its average build year (1982) matches the Illinois average (1979).

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

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

The 5 Illinois counties nearest Knox County in number of bridges, with their condition splits. Its 11.2% Poor share is the 5th-lowest of these 6. Its average build year of 1982 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 Knox County and the 5 Illinois counties closest to it in inventory size
County Bridges Poor
Franklin County 310 2.6%
Coles County 304 8.9%
Knox County (this page) 304 11.2%
Ford County 302 6.3%
Marion County 296 6.4%
Hancock County 292 20.2%

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

Similar inventory size

Nearest county inventories outside IL (304 bridges here).

Similar average build year

Nearest mean year-built outside IL (1982 here).

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

All 304 Good 150 Fair 120 Poor 34

Poor-condition bridges (34)

TR 57

Poor

Over: TRIB TO WALNUT CREEK

NW-34-T13NR4E, Knox, IL

Built 1900 Load: 0.0 t ADT: 25

EB I-74

Poor

Over: SPOON RIVER & TR238A

9 MI E OF KNOXVILLE, Knox, IL

Built 1968 Load: 15.9 t ADT: 7,700

TR 210

Poor

Over: WALNUT CREEK

N1/2-17-T13NR3E, Knox, IL

Built 1900 Load: 17.5 t ADT: 50

WB I-74

Poor

Over: SPOON R & TR 238A

9 MI E OF KNOXVILLE, Knox, IL

Built 1968 Load: 18.8 t ADT: 7,700

CEDAR ST

Poor

Over: CEDAR FORK CREEK

200 N. CEDAR, Knox, IL

Built 1931 Load: 19.4 t ADT: 50

TR 291

Poor

Over: SWAB RUN CREEK

SW-25-T10NR4E, Knox, IL

Built 1971 Load: 21.7 t ADT: 10

TR 244

Poor

Over: WALNUT CREEK

NE-22-T13NR3E, Knox, IL

Built 1966 Load: 24.3 t ADT: 50

MCCLURE ST

Poor

Over: CEDAR CREEK

SOUTH OF W. MAIN ST., Knox, IL

Built 1956 Load: 24.9 t ADT: 1,850

WB I-74

Poor

Over: IL 17 & BNSF-EXEMPT

0.5 MI W OF WOODHULL, Knox, IL

Built 1967 Load: 25.3 t ADT: 7,500

CH 21

Poor

Over: I-74

3 MI E OF KNOXVILLE, Knox, IL

Built 1967 Load: 25.6 t ADT: 75

TR 263

Poor

Over: TRIB TO SPOON RIVER

NW-24-T10NR3E, Knox, IL

Built 1983 Load: 25.6 t ADT: 50

FAS 396-CH 18

Poor

Over: I-74

3 MI E OF SPOON R, Knox, IL

Built 1968 Load: 27.2 t ADT: 350

APPLETON ROAD

Poor

Over: I-74

6 MI E OF KNOXVILLE, Knox, IL

Built 1967 Load: 27.5 t ADT: 150

HENDERSON RD (CH 3

Poor

Over: I-74

2.5 MI W OF WATAGA, Knox, IL

Built 1965 Load: 27.9 t ADT: 200

TR 6A MERCER CO LI

Poor

Over: TRIB.TO N.HENDERSON

SW-7-T13NR1E, Knox, IL

Built 1965 Load: 27.9 t ADT: 10

ONTARIO ROAD

Poor

Over: I-74

.5 MI N HENDERSON CR, Knox, IL

Built 1966 Load: 28.2 t ADT: 200

US 34

Poor

Over: WALNUT CREEK

1 MI SW OF ALTONA, Knox, IL

Built 1921 Load: 28.2 t ADT: 2,550

TR 249

Poor

Over: HAW CREEK

S.CTR-15-T10NR2E, Knox, IL

Built 1971 Load: 28.2 t ADT: 50

TR 74 FARNHAM ST

Poor

Over: US 34 BYPASS

W OF I-74&34 INTERCH, Knox, IL

Built 1965 Load: 29.2 t ADT: 100

BRICKYARD RD (650

Poor

Over: I-74

1 MI NW KNOXVILLE, Knox, IL

Built 1963 Load: 29.5 t ADT: 250

TR 228

Poor

Over: TRIB TO SPOON RIVER

N.CTR-27-T10NR3E, Knox, IL

Built 1969 Load: 29.8 t ADT: 75

TR 341

Poor

Over: KICKAPOO CREEK

SE-14-T9NR4E, Knox, IL

Built 1974 Load: 29.8 t ADT: 50

RIO ROAD

Poor

Over: I-74

5 MI S WOODHULL, Knox, IL

Built 1966 Load: 30.5 t ADT: 200

ILL 41

Poor

Over: BNSF RR (063729D)

0.5 M N.ST.AUGUSTINE, Knox, IL

Built 1983 Load: 30.5 t ADT: 2,300

US 150

Poor

Over: SPOON RIVER

4 MI W OF ILL 180, Knox, IL

Built 1930 Load: 32.4 t ADT: 1,100

FAS 396

Poor

Over: SWAB RUN CREEK

SW-35-T10NR4E, Knox, IL

Built 1996 Load: 32.4 t ADT: 325

FAS 395-CH 17

Poor

Over: SPOON RIVER

5 MI SE OF GILSON, Knox, IL

Built 2000 Load: 32.4 t ADT: 125

FAU 6838-CH 10

Poor

Over: BNSF RR & GRAVEL RD

NW-27-T11NR1E, Knox, IL

Built 1985 Load: 36.3 t ADT: 3,050

SEMINARY ST

Poor

Over: US 34 BYPASS

1 MI E OF US 150, Knox, IL

Built 1972 Load: 36.9 t ADT: 7,600

EB I-74

Poor

Over: IL 17 & BNSF-EXEMPT

0.5 MI W OF WOODHULL, Knox, IL

Built 1967 Load: 39.2 t ADT: 7,500

LINCOLN PARK DR

Poor

Over: US 34 BYPASS

0.6 MI E OF US 150, Knox, IL

Built 1965 Load: 41.8 t ADT: 900

ILL 116

Poor

Over: CEDAR CREEK

APPR 2M W IL 41, Knox, IL

Built 1975 Load: 45.4 t ADT: 1,100

US 150

Poor

Over: POPE CR

2 M S OF ILL 17, Knox, IL

Built 1951 Load: 48.3 t ADT: 2,350

TR 52

Poor

Over: BRUSH CREEK

NW-13-T10NR1E, Knox, IL

Built 1973 Load: 53.5 t ADT: 100

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.