Total bridges
109
Public highway bridges in Boone County
County profile · official public datasets
Boone County, IL
109 public highway bridges tracked in the FHWA National Bridge Inventory: 56% rated Good, 37.6% Fair, 6.4% Poor.
- 109
- Public bridges
- 56%
- Good condition
- 6.4%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Boone County pairs a better-than-median Poor-condition share among rated counties in the state with a newer average build year than the state inventory.
- Top 33%
- lowest Poor share in state
- 6.4%
- Poor-condition share
- 109
- public highway bridges
- 1986
- 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.
Boone County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Boone County ranks #34 of 102 Illinois counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.4%). Boone County, Illinois contains 109 public highway bridges. Roughly 56% are rated “Good,” 37.6% “Fair,” and 6.4% “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
56%
61 of 109 rated 7-9
Fair condition
37.6%
41 of 109 rated 5-6
Poor condition
6.4%
7 of 109 rated 4 or below
In-state Poor-share rank
#34 of 102
Among Illinois counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 109 NBI-tracked bridges by lowest applicable component rating.
Good 56% (61)
Fair 37.6% (41)
Poor 6.4% (7)
Boone County's Poor-condition bridges carry 16,325 vehicle crossings a day
That is 3.6% of the county's reported daily bridge traffic on 6.5% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 2,332 crossings a day against 4,325 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 108 of 109 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
36.7% of Boone County's bridges have passed the 50-year mark
40 of the 109 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 56% 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 71.7% of the county's Poor-condition bridge traffic
S. APPLETON ROAD over KISHWAUKEE RIVER, built 1964, carries 11,700 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 7-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 16,325 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Boone County's bridges were built
109 bridges with a recorded construction year, grouped by decade
- 1900s 1
1900–1909
1 bridges
- 1940s 1
1940–1949
1 bridges
- 1950s
1950–1959
15 bridges
- 1960s
1960–1969
15 bridges
- 1970s
1970–1979
15 bridges
- 1980s
1980–1989
13 bridges
- 1990s
1990–1999
12 bridges
- 2000s
2000–2009
11 bridges
- 2010s
2010–2019
22 bridges
- 2020s 4
2020–2029
4 bridges
What this shows Construction peaked in the 2010s, when 22 of the county's bridges still in the inventory were built, which is 20.2% of those with a recorded year. That cohort is now 5 to 14 years old in the 2024 inventory. Its average build year is 1986, 7 years newer than the Illinois average of 1979.
How Boone County compares with Illinois's closest counties by inventory size
The 5 Illinois counties nearest Boone County in number of bridges, with their condition splits. Its 6.4% Poor share is the 3rd-lowest of these 6. Its average build year of 1986 against a peer-group mean of 1981 is 5 years newer.
Showing the 5 closest of 101 Illinois counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Johnson County | 118 | 58.5% | 39% | 2.5% | 1979 |
| Schuyler County | 114 | 21.1% | 68.4% | 10.5% | 1981 |
| Jersey County | 113 | 57.5% | 38.1% | 4.4% | 1981 |
| Boone County (this page) | 109 | 56% | 37.6% | 6.4% | 1986 |
| Pulaski County | 108 | 35.2% | 56.5% | 8.3% | 1981 |
| Scott County | 99 | 54.5% | 38.4% | 7.1% | 1983 |
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 Boone 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 Boone County, both outside Illinois so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside IL (109 bridges here).
- Mariposa County, CA · 109 bridges
- Gove County, KS · 109 bridges
- Hodgeman County, KS · 109 bridges
- Trigg County, KY · 109 bridges
Similar average build year
Nearest mean year-built outside IL (1986 here).
- El Paso County, TX · avg 1986 · 783 bridges
- Caddo County, LA · avg 1986 · 682 bridges
- Weld County, CO · avg 1986 · 614 bridges
- Polk County, IA · avg 1986 · 545 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Good-condition bridges (61)
FREE CHURCH ROAD
GoodOver: N KINNIKINNICK CREEK
6.5 MI NE ROSCOE, Boone, IL
Built 1973 Load: 18.1 t ADT: 200
GARDEN PRAIRIE RD
GoodOver: SPRING CREEK
3.5 MI S GARDEN PRAI, Boone, IL
Built 1958 Load: 24.3 t ADT: 175
N BOONE SCHOOL RD
GoodOver: S. KINNIKINNICK CRK.
3.0 MI N CALEDONIA, Boone, IL
Built 1965 Load: 24.3 t ADT: 100
N BOONE SCHOOL RD
GoodOver: S. KINNIKINNICK CRK.
3.0 MI N CALEDONIA, Boone, IL
Built 1965 Load: 24.3 t ADT: 100
GRADE SCHOOL ROAD
GoodOver: N KINNIKINNICK CREEK
8.0 MI NW POPLAR GRO, Boone, IL
Built 1973 Load: 24.6 t ADT: 50
WHEELER RD
GoodOver: BRANCH OF KISHWAUKEE
1.5 MI SE CHERRY VAL, Boone, IL
Built 1959 Load: 25.9 t ADT: 1,450
STONE QUARRY RD
GoodOver: I 90
.5 MI S US 20, Boone, IL
Built 2013 Load: 30.1 t ADT: 1,550
TOWNHALL RD
GoodOver: I 90
2 MI E OF US 20, Boone, IL
Built 2014 Load: 30.8 t ADT: 475
STATE STREET
GoodOver: KISHWAUKEE RIVER
DOWNTOWN BELVIDERE, Boone, IL
Built 2001 Load: 32.4 t ADT: 8,800
ROCKTON RD
GoodOver: N KINNIKINNICK CREEK
6.5 MI NE ROSCOE, Boone, IL
Built 1973 Load: 32.4 t ADT: 250
CRAWFORD ROAD
GoodOver: SPRING CREEK
6.0 MI SE BELVIDERE, Boone, IL
Built 1977 Load: 32.4 t ADT: 250
BELOIT RD
GoodOver: BEAVER CREEK
3.5 MI NW BELVIDERE, Boone, IL
Built 1978 Load: 32.4 t ADT: 3,800
FRUIT FARM ROAD
GoodOver: MOSQUITO CREEK
3.5 MI SE BELVIDERE, Boone, IL
Built 1982 Load: 32.4 t ADT: 25
CARLSON RD
GoodOver: SPRING CREEK
3.0 MI S GARDEN PRAI, Boone, IL
Built 1984 Load: 32.4 t ADT: 325
REEDS CROSSING ROA
GoodOver: MOSQUITO CREEK
4.0 MI SE BELVIDERE, Boone, IL
Built 1983 Load: 32.4 t ADT: 200
GRANGE HALL RD
GoodOver: E BR PISCASAW CR
2.5 M SE POPLAR GROV, Boone, IL
Built 1986 Load: 32.4 t ADT: 50
BLOODS POINT ROAD
GoodOver: CN RR
1.5 MI E WINN CO LN, Boone, IL
Built 1991 Load: 32.4 t ADT: 550
CALEDONIA RD
GoodOver: BEAVER CREEK
2.5 M N. OF BELVIDER, Boone, IL
Built 2003 Load: 32.4 t ADT: 3,350
MARENGO RD (TR 77)
GoodOver: MUD CREEK
1.5 MI N GARDN PRARI, Boone, IL
Built 1994 Load: 32.4 t ADT: 2,000
LAWRENCEVILLE RD
GoodOver: MUD CREEK
1.5MI. NW GARDEN PR., Boone, IL
Built 2000 Load: 32.4 t ADT: 1,400
COUNTY LINE RD
GoodOver: BR PISCASAW CREEK
1.5 MI E OF CAPRON, Boone, IL
Built 2004 Load: 32.4 t ADT: 600
GARDEN PRAIRIE RD
GoodOver: COON CREEK
1.5 MI S GARDEN PR, Boone, IL
Built 2005 Load: 32.4 t ADT: 475
IRENE RD
GoodOver: UNNAMED CREEK
1.5MI S OF US 20, Boone, IL
Built 2007 Load: 32.4 t ADT: 1,650
RIVERSIDE ROAD
GoodOver: BR OF BEAVER CR
3.5MI NE OF BELVIDER, Boone, IL
Built 2007 Load: 32.4 t ADT: 2,350
COUNTY LINE RD
GoodOver: SPRING CREEK
2 MI SE GARDEN PRAIR, Boone, IL
Built 2016 Load: 32.4 t ADT: 100
CENTERVILLE RD
GoodOver: BEAVER CREEK
2 MI W OF CAPRON, Boone, IL
Built 2013 Load: 32.4 t ADT: 150
GARDEN PRAIRIE
GoodOver: KISHWAUKEE RIVER
.5 MI N US 20, Boone, IL
Built 2015 Load: 32.4 t ADT: 2,850
POPLAR GROVE RD
GoodOver: KISHWAUKEE RIVER
NE EDGE OF BELVIDERE, Boone, IL
Built 2020 Load: 32.4 t ADT: 2,200
LIVINGSTON SCHOOL
GoodOver: SOUTH KINNIKINNICK C
3.0 MI N CALEDONIA, Boone, IL
Built 2021 Load: 32.4 t ADT: 50
TOWNLINE RD
GoodOver: BR N KINNINNICK CR
NW CORNER BOONE CO., Boone, IL
Built 1960 Load: 32.4 t ADT: 100
CALEDONIA ROAD
GoodOver: S. KINNIKINNICK CR.
3.3 MI. N. CALEDONIA, Boone, IL
Built 1995 Load: 32.4 t ADT: 1,000
POPLAR GROVE RD
GoodOver: BR. OF BEAVER CREEK
1.75 MI. N. OF IL173, Boone, IL
Built 1998 Load: 32.4 t ADT: 1,350
PEARL STREET RD
GoodOver: KINGSBURY CREEK
AT DEKALB CO. LINE, Boone, IL
Built 1999 Load: 32.4 t ADT: 500
IRENE RD
GoodOver: UNNAMED CRK
0.25 MI S OF US 20, Boone, IL
Built 1900 Load: 32.4 t ADT: 3,200
ORTH ROAD
GoodOver: BR OF BEAVER CREEK
0.6 MI. W. OF IL 76, Boone, IL
Built 2009 Load: 32.4 t ADT: 1,650
ORTH RD
GoodOver: BEAVER CREEK
4.0 MI N BELVIDERE, Boone, IL
Built 2014 Load: 32.4 t ADT: 1,650
TOWN HALL ROAD
GoodOver: UNNAMED STREAM
0.25MI S OF US 20, Boone, IL
Built 2010 Load: 32.4 t ADT: 4,950
FAS-39 (HUNTER RD)
GoodOver: BEAVER CREEK
3.0 MI NW OF CAPRON, Boone, IL
Built 2011 Load: 34.0 t ADT: 1,550
IL 173
GoodOver: BR. BEAVER CREEK
2.7 MI. E. OF IL 76, Boone, IL
Built 2000 Load: 35.0 t ADT: 4,100
PEARL ST
GoodOver: I 90
4 MI E OF US 20, Boone, IL
Built 2014 Load: 35.6 t ADT: 750
TRIPP RD
GoodOver: I-90
.5 MI S OF US 20, Boone, IL
Built 2016 Load: 37.3 t ADT: 300
COUNTY LINE RD
GoodOver: I 90
MC HENRY CO LINE, Boone, IL
Built 2014 Load: 38.6 t ADT: 250
SPRING CENTER RD
GoodOver: I 90
3 MI W MCHENRY CO, Boone, IL
Built 2016 Load: 39.5 t ADT: 75
IRENE RD
GoodOver: I 90
.5 MI S US 20, Boone, IL
Built 2013 Load: 40.5 t ADT: 1,650
IL 173
GoodOver: WILLOW CREEK
0.3 MI E WINN. CO LN, Boone, IL
Built 1994 Load: 42.1 t ADT: 6,250
SHATTUCK RD
GoodOver: I 90
2.5 MI W MCHENRY CO, Boone, IL
Built 2014 Load: 42.1 t ADT: 350
GENOA RD- FAS 37
GoodOver: I 90
.6 MI S OF US 20, Boone, IL
Built 2014 Load: 42.4 t
DENNY RD
GoodOver: GERYLINE CR
3.5 MI SE POPLAR GROVE, Boone, IL
Built 2021 Load: 42.8 t ADT: 300
JOHNSON RD
GoodOver: I 90
.5 MI S CHRYSLER DR, Boone, IL
Built 2014 Load: 43.1 t ADT: 150
IL 173
GoodOver: PISCASAW CREEKTRIB.
AT MCHENRY CO. LN., Boone, IL
Built 2001 Load: 45.4 t ADT: 5,000
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.