County profile · official public datasets

Cass County, IL

77 public highway bridges tracked in the FHWA National Bridge Inventory: 29.9% rated Good, 50.6% Fair, 19.5% Poor.

77
Public bridges: 29.9%
Good condition: 19.5%
Poor condition

The verdict

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

Cass County pairs a higher-than-median Poor-condition share among rated counties in the state with a newer average build year than the state inventory.

97th
of 102 on Poor share: 19.5%
Poor-condition share: 77
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.

Cass County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Cass County ranks #97 of 102 Illinois counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 19.5%). Cass County, Illinois contains 77 public highway bridges. Roughly 29.9% are rated “Good,” 50.6% “Fair,” and 19.5% “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

Public highway bridges in Cass County

Good condition

29.9%

23 of 77 rated 7-9

Fair condition

50.6%

39 of 77 rated 5-6

Poor condition

19.5%

15 of 77 rated 4 or below

In-state Poor-share rank

#97 of 102

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

Condition distribution

Share of 77 NBI-tracked bridges by lowest applicable component rating.

Good

29.9% (23)

Fair

50.6% (39)

Poor

19.5% (15)

Cass County's Poor-condition bridges carry 10,975 vehicle crossings a day

That is 21.4% of the county's reported daily bridge traffic on 19.5% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 732 crossings a day against 948 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 77 of 77 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

26% of Cass County's bridges have passed the 50-year mark

20 of the 77 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 29.9% 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 51% of the county's Poor-condition bridge traffic

US 67 / IL 100 over ILLINOIS RIVER, built 1955, carries 5,600 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 15-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 10,975 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1930s

3
1940s

2
1950s

6
1960s

6
1970s

8
1980s

16
1990s

12
2000s

13
2010s

8
2020s

3

What this shows Construction peaked in the 1980s, when 16 of the county's bridges still in the inventory were built, which is 20.8% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year is 1986, 7 years newer than the Illinois average of 1979.

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

The 5 Illinois counties nearest Cass County in number of bridges, with their condition splits. Its 19.5% Poor share is the 6th-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.

Bridge inventory size and condition shares for Cass County and the 5 Illinois counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Mason County	86	33.7%	61.6%	4.7%	1980
Gallatin County	82	78%	13.4%	8.5%	1984
Calhoun County	81	53.1%	43.2%	3.7%	1983
Edwards County	79	64.6%	27.8%	7.6%	1982
Cass County (this page)	77	29.9%	50.6%	19.5%	1986
Brown County	71	47.9%	38%	14.1%	1975

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

Similar inventory size

Nearest county inventories outside IL (77 bridges here).

Clear Creek County, CO · 77 bridges
Liberty County, FL · 77 bridges
Appling County, GA · 77 bridges
Baldwin County, GA · 77 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.

All 77 Good 23 Fair 39 Poor 15

All bridges (77)

Sort:

Cass County Bridge Snapshot

Condition distribution

Cass County's Poor-condition bridges carry 10,975 vehicle crossings a day

26% of Cass County's bridges have passed the 50-year mark

One structure carries 51% of the county's Poor-condition bridge traffic

How Cass 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 (77)

FAS 577

TR 106

FAS577

FAS 579

US 67 / ILL 100

FAS577

S MAIN ST

TR 30

FAS 575

FAS577

FAS 575

TR 65A

TR 48

TR 67

OLD IL 125 (TR59)

TR 7

GARNER RD.

FAS 573

TR 39

TR 83

TR 28B

TR 133

TR 135

TR 12

TR 54

KIRCHER RD TR 44

TR 52

GRIDLEY RD - TR 89

TR 43

TR 54 FAS 581

TR-95

TR 84

EILER ROAD - TR 21

TR-130

TR 102

TR 82 SWEATMAN RD

IL 125

IL 78

TR 118

CH 11

CH 11

FAS1576

FAS 580

TR 20

TR-105

TR 163

TR 142

TR 23

FRONT/HARDIN STREE

IL 78

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