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

Fair-condition bridges (59)

GRASSY ROAD

Fair

Over: LITTLE GRASSY LK SPILLWY

10.0 MI SW OF HDQRTRS, Williamson, IL

Built 1939 Load: 7.3 t ADT: 800

TR 608

Fair

Over: MINE HAULAGE ROAD

1 MI N OF ILL 13, Williamson, IL

Built 1978 Load: 16.5 t ADT: 250

WOLF CREEK ROAD

Fair

Over: CRAB ORCHARD LAKE

2.5 MI SW OF HDQRTRS, Williamson, IL

Built 1938 Load: 17.2 t ADT: 150

CS 7000 OFF FAS 90

Fair

Over: DRAINAGE DITCH

0.7 M W JOHNSTON CIT, Williamson, IL

Built 1956 Load: 19.8 t ADT: 800

NO. DEVILS KITCHEN

Fair

Over: GRASSY CREEK

SEC 16 T10S R1E, Williamson, IL

Built 1959 Load: 20.0 t ADT: 200

FAS 904

Fair

Over: CRAB ORCHARD CREEK

0.67 MI SO PITTSBURG, Williamson, IL

Built 1972 Load: 22.7 t ADT: 2,850

WILDCAT DRIVE

Fair

Over: TRIB TO CRAB ORCH CK

SOUTH EDGE OF MARION, Williamson, IL

Built 1980 Load: 24.3 t ADT: 2,700

BOYTON ST

Fair

Over: DRAINAGE DITCH

BOYTON E OF PARK DR, Williamson, IL

Built 1967 Load: 24.3 t ADT: 2,400

FAS 903 (UNMARKED)

Fair

Over: BEAR CREEK

2 MI W JOHNSTON CITY, Williamson, IL

Built 1956 Load: 24.9 t ADT: 6,000

FAS 903 (UNMARKED)

Fair

Over: LAKE CREEK

1 MI W JOHNSTON CITY, Williamson, IL

Built 1956 Load: 25.6 t ADT: 6,000

TR 350

Fair

Over: LAKE CREEK

.5 MI S JOHNSTON CTY, Williamson, IL

Built 1978 Load: 26.6 t ADT: 325

I 24 EB

Fair

Over: INTERSTATE 57

PULLEYS MILL INTER, Williamson, IL

Built 1972 Load: 27.9 t ADT: 11,150

TR 4

Fair

Over: STREAM

N E CORNER WSON CO, Williamson, IL

Built 1900 Load: 28.2 t ADT: 75

ILL 148

Fair

Over: MIDDLE WOLF CREEK

2.3 MI N OF I-57, Williamson, IL

Built 1962 Load: 29.2 t ADT: 5,600

ILL 166

Fair

Over: S FORK SALINE RELIEF

3.3 MI S OF ILL 13, Williamson, IL

Built 1934 Load: 29.8 t ADT: 3,000

ILL 148

Fair

Over: BIG MUDDY RIVER

0.1 MI S FRANKLIN CO, Williamson, IL

Built 1931 Load: 30.1 t ADT: 3,650

ILL 166

Fair

Over: STREAM

2.7 MI SO OF ILL 13, Williamson, IL

Built 1934 Load: 31.1 t ADT: 3,000

ILL 13 EB

Fair

Over: CRABORCHARD CREEK

1 MI E OF MARION, Williamson, IL

Built 1962 Load: 32.1 t ADT: 13,800

ILL 13 WB

Fair

Over: CRABORCHARD CREEK

1 MI E OF MARION, Williamson, IL

Built 1962 Load: 32.1 t ADT: 13,800

TR 29

Fair

Over: POND CREEK

2 MI. NW CORINTH, Williamson, IL

Built 1977 Load: 32.4 t ADT: 75

TR 423

Fair

Over: LITTLE GRASSY CREEK

6 MI SW OF CARTERVIL, Williamson, IL

Built 1978 Load: 32.4 t ADT: 650

TR 509

Fair

Over: LITTLE WOLF CREEK

3 MI NW PULLEYS MILL, Williamson, IL

Built 1986 Load: 32.4 t ADT: 25

TR 278

Fair

Over: LITTLE SALINE CREEK

0200N-1050E, Williamson, IL

Built 1990 Load: 32.4 t ADT: 50

TR 552

Fair

Over: POND CREEK

5 MI N OF PITTSBURG, Williamson, IL

Built 1994 Load: 32.4 t ADT: 125

OLD IL 13-MAIN ST

Fair

Over: STREAM AT ECL MARION

NEAR ECL OF MARION, Williamson, IL

Built 2003 Load: 32.4 t ADT: 3,800

CH 4 (STOTLAR RD)

Fair

Over: INTERSTATE 57

0.7 MI W OF ILL 37, Williamson, IL

Built 1961 Load: 33.0 t ADT: 2,650

CH 13/S MARKET ST

Fair

Over: CRAB ORCHARD CR

AT SCL MARION, Williamson, IL

Built 1986 Load: 33.0 t ADT: 3,550

FAS 907 (CH 9)(UNM

Fair

Over: BIG MUDDY RIVER

1 MI S OF HURST, Williamson, IL

Built 1937 Load: 33.7 t ADT: 5,550

NEW IL 13 EB

Fair

Over: BANKSTON FORK

1.7 MI W SALINE CO, Williamson, IL

Built 1994 Load: 35.0 t ADT: 9,000

ILL 13 WB

Fair

Over: CRAB ORCHARD LAKE

1.6 MI E JACKSON CO, Williamson, IL

Built 1939 Load: 35.3 t ADT: 23,500

CH 1

Fair

Over: LAKE CREEKOVERFLOW

SW CORP LIM J CITY, Williamson, IL

Built 1979 Load: 35.3 t ADT: 600

ILL 148

Fair

Over: POND CREEK

1.1 MI S FRANKLIN CO, Williamson, IL

Built 1931 Load: 35.6 t ADT: 3,650

ILL 13 WB

Fair

Over: CRAB ORCHARD LAKE

1.1 MI E JACKSON CO, Williamson, IL

Built 1939 Load: 36.6 t ADT: 25,600

NEW ILL RTE 13

Fair

Over: L CRAB ORCHARD CR

CRAB ORCHARD, Williamson, IL

Built 1990 Load: 37.3 t ADT: 12,100

ILL 13

Fair

Over: DRAINAGE DITCH

0.1 M E OF ILL 166, Williamson, IL

Built 1962 Load: 37.9 t ADT: 12,100

ILL 37

Fair

Over: CRAB ORCHARD CREEK

SCL MARION, Williamson, IL

Built 1997 Load: 38.6 t ADT: 5,500

ILL 13

Fair

Over: STREAM E OF MARION

0.5 MI E OF MARION, Williamson, IL

Built 1962 Load: 39.9 t ADT: 13,800

FAS 904

Fair

Over: LITTLE CRAB ORCHARD

2.06 MI SO PITTSBURG, Williamson, IL

Built 1972 Load: 39.9 t ADT: 2,950

TR 140

Fair

Over: HURRICANE CREEK

0.5 MILE N OF COLP, Williamson, IL

Built 1981 Load: 40.5 t ADT: 150

ILL 166

Fair

Over: SUGAR CREEK

AT ECL CREAL SPRINGS, Williamson, IL

Built 1933 Load: 42.4 t ADT: 1,400

I 57 NB

Fair

Over: OLD ROUTE 13

IN MARION, Williamson, IL

Built 2009 Load: 43.7 t ADT: 17,350

I-24 RAMP 0.94

Fair

Over: I-57

PULLEYS MILL INTER, Williamson, IL

Built 1972 Load: 44.1 t ADT: 100

I 57 SB

Fair

Over: OLD ROUTE 13

IN MARION, Williamson, IL

Built 2009 Load: 44.7 t ADT: 15,400

I 57 NB

Fair

Over: CRAB ORCHARD CREEK

2 MI S OLD IL 13, Williamson, IL

Built 2006 Load: 45.7 t ADT: 17,350

I 57 SB

Fair

Over: CRAB ORCHARD CREEK

2 MI S OLD IL 13, Williamson, IL

Built 2006 Load: 45.7 t ADT: 17,350

FAS 1901

Fair

Over: CRAB ORCHARD SPILWAY

4 MI.SW CARTERVILLE, Williamson, IL

Built 1976 Load: 46.3 t ADT: 1,300

EB IL 13

Fair

Over: BNSF RR

1.3 MILES WEST I-57, Williamson, IL

Built 2014 Load: 46.7 t ADT: 26,300

SBI 13 (UNMARKED)

Fair

Over: PIGEON CREEK

1.1 MI W OF ILL 148, Williamson, IL

Built 1920 Load: 47.0 t ADT: 1,550

IL 148-FAP 726

Fair

Over: LITTLE WOLF CREEK

3.3 MI N OF I-57, Williamson, IL

Built 1958 Load: 48.6 t ADT: 6,150

I-57 SB

Fair

Over: IL 13

S OF NCL MARION, Williamson, IL

Built 2013 Load: 49.9 t ADT: 14,700

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.