Total bridges
304
Public highway bridges in Knox County
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.
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
- 1900s 15
1900–1909
15 bridges
- 1920s 6
1920–1929
6 bridges
- 1930s 7
1930–1939
7 bridges
- 1950s 5
1950–1959
5 bridges
- 1960s
1960–1969
47 bridges
- 1970s
1970–1979
35 bridges
- 1980s
1980–1989
54 bridges
- 1990s
1990–1999
56 bridges
- 2000s
2000–2009
34 bridges
- 2010s
2010–2019
35 bridges
- 2020s 10
2020–2029
10 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).
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.
| 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.
Fair-condition bridges (120)
US 34 WB
FairOver: US 150
N CL OF GALESBURG, Knox, IL
Built 1965 Load: 51.5 t ADT: 9,100
ILL 8
FairOver: STREAM
4.5 MI E OF ILL 97, Knox, IL
Built 1971 Load: 51.5 t ADT: 900
WB US 34
FairOver: CEDAR CREEK
SW EDGE OF GALESBURG, Knox, IL
Built 1979 Load: 52.2 t ADT: 8,950
IL 180
FairOver: CADWELL CR
1.5 MI N WILLIAMSFLD, Knox, IL
Built 2000 Load: 52.2 t ADT: 400
US 34 EB
FairOver: US 150
N CL OF GALESBURG, Knox, IL
Built 1965 Load: 53.1 t ADT: 12,900
FAI 74EB
FairOver: HENDERSON CREEK
5.4 MI S HENRY CO LI, Knox, IL
Built 2015 Load: 54.8 t ADT: 8,150
TR 320
FairOver: TRIB TO FITCH CR
SW-24-T13NR4E, Knox, IL
Built 1986 Load: 54.8 t ADT: 10
FAI 74WB
FairOver: HENDERSON CREEK
5.4 MI S HENRY CO LI, Knox, IL
Built 2015 Load: 55.1 t ADT: 8,150
US 150
FairOver: INTERSTATE 74
1 MI E OF KNOXVILLE, Knox, IL
Built 1963 Load: 57.0 t ADT: 2,600
COUNTY HIGHWAY 37
FairOver: TRIB.S.HENDERSON.CRK
SE-16-T12NR1E, Knox, IL
Built 1960 Load: 57.3 t ADT: 500
FAI 74 EB
FairOver: Pope Creek
0.9mi S Henry Co Ln, Knox, IL
Built 2018 Load: 63.5 t ADT: 8,150
US 150 (MAIN ST)
FairOver: CEDAR CREEK BNSF RR
500 BLK W. MAIN, Knox, IL
Built 2012 Load: 64.2 t ADT: 10,300
BROAD STREET
FairOver: CEDAR CREEK CHANNEL
N.OF WATER ST., Knox, IL
Built 1930 Load: 67.1 t ADT: 1,550
I-74
FairOver: STREAM
.1M N KNOX CO LINE, Knox, IL
Built 1967 Load: 88.8 t ADT: 15,000
US 34
FairOver: CEDAR CREEK
0.7M E OF COUNTY LN, Knox, IL
Built 1986 Load: 88.8 t ADT: 8,950
I74WB REST AREA RA
FairOver: TRIB SPOON RIVER
SPOON RIVER RESTAREA, Knox, IL
Built 1976 Load: 89.1 t ADT: 500
COUNTY HIGHWAY 07
FairOver: MIDDLE CREEK
NE-4-T11NR2E, Knox, IL
Built 1956 Load: 89.1 t ADT: 325
TR 325
FairOver: HERMON CREEK
NE-17-T9NR2E, Knox, IL
Built 1975 Load: 89.1 t ADT: 25
FAS 398 - CH 20
FairOver: TRIB TO HAW CREEK
NW-1-T9NR2E, Knox, IL
Built 1973 Load: 89.1 t ADT: 100
STATE ST
FairOver: COURT CREEK
STATE&ATSFRR, Knox, IL
Built 1992 Load: 89.1 t ADT: 1,300
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.