County profile · official public datasets

DeKalb County, IL

261 public highway bridges tracked in the FHWA National Bridge Inventory: 40.6% rated Good, 46.4% Fair, 13% Poor.

261
Public bridges: 40.6%
Good condition: 13%
Poor condition

The verdict

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

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

86th
of 102 on Poor share: 13%
Poor-condition share: 261
public highway bridges: 1981
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.

DeKalb County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, DeKalb County ranks #86 of 102 Illinois counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 13%). DeKalb County, Illinois contains 261 public highway bridges. Roughly 40.6% are rated “Good,” 46.4% “Fair,” and 13% “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

261

Public highway bridges in DeKalb County

Good condition

40.6%

106 of 261 rated 7-9

Fair condition

46.4%

121 of 261 rated 5-6

Poor condition

13%

34 of 261 rated 4 or below

In-state Poor-share rank

#86 of 102

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

Condition distribution

Share of 261 NBI-tracked bridges by lowest applicable component rating.

Good

40.6% (106)

Fair

46.4% (121)

Poor

13% (34)

DeKalb County's Poor-condition bridges carry 47,635 vehicle crossings a day

That is 8.1% of the county's reported daily bridge traffic on 13.1% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 1,401 crossings a day against 2,608 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 260 of 261 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

39.8% of DeKalb County's bridges have passed the 50-year mark

104 of the 261 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 40.6% 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 28.6% of the county's Poor-condition bridge traffic

Annie Glidden Rd. over Watson Creek, built 1971, carries 13,600 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 47,635 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1920s

2
1930s

5
1940s

8
1950s

29
1960s

33
1970s

41
1980s

45
1990s

37
2000s

35
2010s

18
2020s

8

What this shows Construction peaked in the 1980s, when 45 of the county's bridges still in the inventory were built, which is 17.2% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year (1981) matches the Illinois average (1979).

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

The 5 Illinois counties nearest DeKalb County in number of bridges, with their condition splits. Its 13% Poor share is the 5th-lowest of these 6. Its average build year of 1981 against a peer-group mean of 1980 is in line with the group.

Showing the 5 closest of 101 Illinois counties eligible for comparison.

Bridge inventory size and condition shares for DeKalb County and the 5 Illinois counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Grundy County	269	40.5%	32.7%	26.8%	1984
Wayne County	266	54.1%	36.8%	9%	1982
Montgomery County	261	52.1%	40.6%	7.3%	1977
DeKalb County (this page)	261	40.6%	46.4%	13%	1981
Jefferson County	260	47.7%	46.2%	6.2%	1984
Effingham County	253	47.4%	47.8%	4.7%	1974

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

Similar inventory size

Nearest county inventories outside IL (261 bridges here).

Russell County, KS · 261 bridges
Vermilion County, LA · 261 bridges
Camden County, NJ · 261 bridges
Doña Ana County, NM · 261 bridges

Similar average build year

Nearest mean year-built outside IL (1981 here).

Franklin County, OH · avg 1981 · 922 bridges
Greenville County, SC · avg 1981 · 635 bridges
Montgomery County, OH · avg 1981 · 632 bridges
Shawnee County, KS · avg 1981 · 563 bridges

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

All 261 Good 106 Fair 121 Poor 34

All bridges (261)

Sort:

DeKalb County Bridge Snapshot

Condition distribution

DeKalb County's Poor-condition bridges carry 47,635 vehicle crossings a day

39.8% of DeKalb County's bridges have passed the 50-year mark

One structure carries 28.6% of the county's Poor-condition bridge traffic

How DeKalb 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

All bridges (261)

TR-171 (OWENS RD)

BARCHARD ROAD

ANDERLAND RD

KIRKLAND RD

NEW LEBANON RD

IRENE RD

PLEASANT HILL ROAD

MILLER RD

LEE ROAD

GLIDDEN RD

TOWER ROAD

E PAW PAW RD

FAIRVIEW DRIVE

UNIVERSITY RD

UNIVERSITY RD

W. COUNTY LINE RD

IL 64 FAP 17

LELAND RD

LASHER ROAD

IL 23

HAUMESSER RD

SHABBONA GROVE RD

LASHER ROAD

HINCKLEY RD

ROLLO RD

KIRKLAND ROAD

HOWISON RD

HOUGHTBY RD

PERRY RD

MCGIRR RD

SLEEPY HOLLOW RD

IRENE RD

PLANK ROAD

S MALTA RD

CHASE ROAD/TR196A

PRESERVE RD

SHABBONA GROVE RD

E SANDWICH RD

BARBER GREENE RD

FAS 1112 UNIVERSIT

THOMPSON ROAD

WOLF RD

SHABBONA GROVE RD

FAP 324 - PEACE RD

GOBLE RD

HILLCREST DRIVE

CHICAGO RD

SUYDAM RD

SOMONAUK ROAD

SOMONAUK ROAD

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