County profile · official public datasets

Williamson County, IL

201 public highway bridges tracked in the FHWA National Bridge Inventory: 67.2% rated Good, 29.4% Fair, 3.5% Poor.

201
Public bridges
67.2%
Good condition
3.5%
Poor condition

The verdict

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

Williamson County pairs a top-10% lowest Poor-condition share among rated counties in the state with a newer average build year than the state inventory.

Top 7%
lowest Poor share in state
3.5%
Poor-condition share
201
public highway bridges
1985
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.

Williamson County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Williamson County ranks #7 of 102 Illinois counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 3.5%). Williamson County, Illinois contains 201 public highway bridges. Roughly 67.2% are rated “Good,” 29.4% “Fair,” and 3.5% “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

201

Public highway bridges in Williamson County

Good condition

67.2%

135 of 201 rated 7-9

Fair condition

29.4%

59 of 201 rated 5-6

Poor condition

3.5%

7 of 201 rated 4 or below

In-state Poor-share rank

#7 of 102

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

Condition distribution

Share of 201 NBI-tracked bridges by lowest applicable component rating.

Good
67.2% (135)
Fair
29.4% (59)
Poor
3.5% (7)

Williamson County's Poor-condition bridges carry 59,625 vehicle crossings a day

That is 6.8% of the county's reported daily bridge traffic on 3.5% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 8,518 crossings a day against 2,662 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 200 of 201 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

25.9% of Williamson County's bridges have passed the 50-year mark

52 of the 201 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 67.2% 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 42.9% of the county's Poor-condition bridge traffic

ILL 13 EB over CRABORCHARD LAKE, built 1964, carries 25,600 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 7-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 59,625 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

When Williamson County's bridges were built

201 bridges with a recorded construction year, grouped by decade

bridges

What this shows Construction peaked in the 1990s, when 43 of the county's bridges still in the inventory were built, which is 21.4% of those with a recorded year. That cohort is now 25 to 34 years old in the 2024 inventory. Its average build year is 1985, 6 years newer than the Illinois average of 1979.

Source FHWA National Bridge Inventory (year built) As of 2024 NBI release

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

The 5 Illinois counties nearest Williamson County in number of bridges, with their condition splits. Its 3.5% Poor share is the 1st-lowest of these 6. Its average build year of 1985 against a peer-group mean of 1980 is 5 years newer.

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

Bridge inventory size and condition shares for Williamson County and the 5 Illinois counties closest to it in inventory size
County Bridges Poor
Fulton County 210 21%
McDonough County 209 6.7%
Williamson County (this page) 201 3.5%
Warren County 199 7.5%
Crawford County 197 6.1%
Jo Daviess County 193 9.8%

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

Similar inventory size

Nearest county inventories outside IL (201 bridges here).

Similar average build year

Nearest mean year-built outside IL (1985 here).

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

All 201 Good 135 Fair 59 Poor 7

Good-condition bridges (135)

TR 556

Good

Over: LAKE CREEK

1.5 MI NW PITTSBURG, Williamson, IL

Built 1987 Load: 38.9 t ADT: 75

ILL 166

Good

Over: S FORK SALINE RIVER

3.6 MI S OF ILL 13, Williamson, IL

Built 1991 Load: 39.2 t ADT: 2,100

CS 1108-CHAMPIONS

Good

Over: UNNAMED STREAM

KOKOPELLI SUBDVSION, Williamson, IL

Built 1996 Load: 39.2 t ADT: 600

CH 1

Good

Over: LAKE CREEK

.5 MI SW JOHNSTON CY, Williamson, IL

Built 1979 Load: 39.5 t ADT: 600

SBI 13B (UNMARKED)

Good

Over: BR.L.CRAB ORCHARD CR

.09 mi w Saraville R, Williamson, IL

Built 2012 Load: 40.2 t ADT: 1,600

TR 9

Good

Over: STREAM

4 MI NE OF CORINTH, Williamson, IL

Built 1991 Load: 40.2 t ADT: 100

LAKE OF EGYPT RD

Good

Over: LAKE EGYPT SPILLWAY

6 MI S MARION, Williamson, IL

Built 1962 Load: 40.5 t ADT: 2,800

FAS 1887-CH 12

Good

Over: SUGAR CREEK

7 MI S CRAB ORCHARD, Williamson, IL

Built 1995 Load: 41.1 t ADT: 500

FAS 1900

Good

Over: LITTLE WOLF CREEK

4 MI NW PULLEYS MILL, Williamson, IL

Built 1942 Load: 41.5 t ADT: 2,100

ILL 37

Good

Over: BNSF RR

1.7 MI N OF ILL 148, Williamson, IL

Built 2009 Load: 41.8 t ADT: 3,350

FAS 908

Good

Over: LITTLE HURRICANE CR

0.3 MI E OF COLP, Williamson, IL

Built 2001 Load: 42.1 t ADT: 5,700

THE HILL AVE

Good

Over: I-57

0.43 MI E HALFWAY RD, Williamson, IL

Built 2014 Load: 42.1 t ADT: 3,600

SKYHAWK RD

Good

Over: UNNAMED CREEK

8 MI SE CARBONDALE, Williamson, IL

Built 2013 Load: 42.1 t ADT: 650

HERRIN ROAD

Good

Over: TRIB TO POND CREEK

0.75M E HERRIN, Williamson, IL

Built 2016 Load: 42.8 t ADT: 6,200

WB IL 13

Good

Over: BNSF RR

MARION, Williamson, IL

Built 2015 Load: 43.1 t ADT: 26,300

FAS 2904

Good

Over: LITTLE SALINE CREEK

2 MI NE PULLEYS MILL, Williamson, IL

Built 1983 Load: 43.1 t ADT: 3,850

GERMAN CHURCH RD

Good

Over: CREEK

1 MI NE JOHNSTON CIT, Williamson, IL

Built 2019 Load: 43.7 t ADT: 225

NEW IL 13 (WB)

Good

Over: BANKSTON FORK

1.7 MI W SALINE CO L, Williamson, IL

Built 1990 Load: 44.1 t ADT: 9,000

PLEASANT VALLEY RD

Good

Over: GRASSY CREEK

1 MI W OF STONEFORT, Williamson, IL

Built 2014 Load: 44.1 t ADT: 175

HERRIN ROAD

Good

Over: TRIB TO POND CREEK

1.0M E HERRIN, Williamson, IL

Built 2016 Load: 46.0 t ADT: 5,700

WB IL 13

Good

Over: MARATHON DR

MARION, Williamson, IL

Built 2015 Load: 46.0 t ADT: 26,300

EB IL 13

Good

Over: MARATHON DR

MARION, Williamson, IL

Built 2014 Load: 46.0 t ADT: 26,300

IL 148

Good

Over: WOLF CREEK

I MI N OF I-57, Williamson, IL

Built 2021 Load: 47.6 t ADT: 5,600

FAS 1901

Good

Over: LITTLE GRASSY CREEK

4 MI S OF CARTERVILL, Williamson, IL

Built 1976 Load: 50.9 t ADT: 850

A-3 ROAD

Good

Over: PIGEON CREEK

0.5 MI NW OF HDQRTRS, Williamson, IL

Built 1990 Load: 51.7 t ADT: 400

FAS 2887-IL 37

Good

Over: LAKE CREEK

0.4 M S JHNSTON CITY, Williamson, IL

Built 2000 Load: 52.8 t ADT: 8,000

IL 148-FAP 726

Good

Over: WOLF CREEK

1.5 MI N FAS 1900, Williamson, IL

Built 2001 Load: 54.8 t ADT: 6,150

LIMB BRANCH LANE

Good

Over: LIMB BRANCH CREEK

1.5 MI S MARION, Williamson, IL

Built 2021 Load: 54.8 t ADT: 100

MORGAN AVE TO I-57

Good

Over: IL 13

S OF NCL MARION, Williamson, IL

Built 2015 Load: 57.0 t ADT: 1,250

LIMB BRANCH LA

Good

Over: BNSF RR

0.5 MI. W. ILL. 37, Williamson, IL

Built 2019 Load: 60.6 t ADT: 100

WESTMINSTER DR

Good

Over: I-57

0.25 MI E WCL MARION, Williamson, IL

Built 2023 Load: 62.9 t ADT: 2,250

FAS 908 (CH 11)

Good

Over: TRIB TO HURRICANE CR

0.5 MI E OF COLP, Williamson, IL

Built 2001 Load: 63.8 t ADT: 5,700

I-57NB TO MORGAN A

Good

Over: IL 13 EB TO I-57 NB

S OF NCL MARION, Williamson, IL

Built 2015 Load: 73.2 t ADT: 800

ILL 37

Good

Over: LITTLE SALINE CREEK

NEAR PULLEYS MILL, Williamson, IL

Built 2009 Load: 77.8 t ADT: 4,600

NEW ILL RTE 13

Good

Over: SALT CREEK

0.4 M W OF SALINE CO, Williamson, IL

Built 1990 Load: 89.1 t ADT: 9,000

Read our methodology - how this data is sourced, computed, and verified.

Related

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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.