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.

1900s

15
1920s

6
1930s

7
1950s

5
1960s

47
1970s

35
1980s

54
1990s

56
2000s

34
2010s

35
2020s

10

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).

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	Good	Fair	Poor	Avg. built
Franklin County	310	77.1%	20.3%	2.6%	1983
Coles County	304	39.5%	51.6%	8.9%	1981
Knox County (this page)	304	49.3%	39.5%	11.2%	1982
Ford County	302	55.6%	38.1%	6.3%	1983
Marion County	296	62.5%	31.1%	6.4%	1973
Hancock County	292	41.8%	38%	20.2%	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 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).

Marshall County, IA · 304 bridges
Osage County, KS · 304 bridges
Nobles County, MN · 304 bridges
Lincoln County, TN · 304 bridges

Similar average build year

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

Oklahoma County, OK · avg 1982 · 1,216 bridges
Jackson County, MO · avg 1982 · 930 bridges
Milwaukee County, WI · avg 1982 · 893 bridges
Broward County, FL · avg 1982 · 686 bridges

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

Good-condition bridges (150)

Sort:

Knox County Bridge Snapshot

Condition distribution

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

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

One structure carries 13.8% of the county's Poor-condition bridge traffic

How Knox 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

Good-condition bridges (150)

TR 192

TR 84

FAS 393-CH 4

TR 194

FAS 394-CH 12

TR 84

HENDERSON ST

TR 260

TR 32

TR 195B

TR 289

TR 79

TR 79

TR 261

TR 56

TR 2 CO LINE ROAD

TR 279

TR 98

TR 260

TR 259

TR 254

TR 172

TR 6

TR 187

TR 112

TR 130

TR 154

TR 56A

TR 15

CO HWY 2

TR 114

TR 320

TR 76

TR 250

TR 359

CH 19

TR 318

TR 305

TR 175

TR 8

TR 56A

TR 152

FAS 394 - CH 12

TR 240

TR 94

TR 192A

FAS 394 - CH 12

CH 19

FAS 1395-CH 6

TR 324

Related