County profile · official public datasets

St. Clair County, IL

486 public highway bridges tracked in the FHWA National Bridge Inventory: 50% rated Good, 40.9% Fair, 9.1% Poor.

486
Public bridges
50%
Good condition
9.1%
Poor condition

The verdict

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

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

68th
of 102 on Poor share
9.1%
Poor-condition share
486
public highway bridges
1977
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.

St. Clair County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, St. Clair County ranks #68 of 102 Illinois counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 9.1%). St. Clair County, Illinois contains 486 public highway bridges. Roughly 50% are rated “Good,” 40.9% “Fair,” and 9.1% “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

486

Public highway bridges in St. Clair County

Good condition

50%

243 of 486 rated 7-9

Fair condition

40.9%

199 of 486 rated 5-6

Poor condition

9.1%

44 of 486 rated 4 or below

In-state Poor-share rank

#68 of 102

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

Condition distribution

Share of 486 NBI-tracked bridges by lowest applicable component rating.

Good
50% (243)
Fair
40.9% (199)
Poor
9.1% (44)

St. Clair County's Poor-condition bridges carry 535,350 vehicle crossings a day

That is 10% of the county's reported daily bridge traffic on 9.1% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 12,167 crossings a day against 9,231 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 484 of 486 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

46.1% of St. Clair County's bridges have passed the 50-year mark

224 of the 486 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 50% 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 22% of the county's Poor-condition bridge traffic

I-55/64; US 40 PSC over TRRA, built 1966, carries 117,700 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 44-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 535,350 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

When St. Clair County's bridges were built

486 bridges with a recorded construction year, grouped by decade

bridges

What this shows Construction peaked in the 1960s, when 84 of the county's bridges still in the inventory were built, which is 17.3% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1977) matches the Illinois average (1979).

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

How St. Clair County compares with Illinois's closest counties by inventory size

The 5 Illinois counties nearest St. Clair County in number of bridges, with their condition splits. Its 9.1% Poor share is the 5th-lowest of these 6. Its average build year of 1977 against a peer-group mean of 1979 is in line with the group.

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

Bridge inventory size and condition shares for St. Clair County and the 5 Illinois counties closest to it in inventory size
County Bridges Poor
LaSalle County 528 12.3%
Madison County 523 8.4%
Vermilion County 494 7.3%
St. Clair County (this page) 486 9.1%
Winnebago County 467 7.1%
Sangamon County 466 6.2%

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

Similar inventory size

Nearest county inventories outside IL (486 bridges here).

Similar average build year

Nearest mean year-built outside IL (1977 here).

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

All 486 Good 243 Fair 199 Poor 44

Good-condition bridges (243)

ILL 159

Good

Over: RICHLAND CREEK

IN BELLEVILLE, St. Clair, IL

Built 1923 Load: 41.1 t ADT: 11,400

IL 161

Good

Over: Schoenberger Creek

300 NW DUTCH HOLLOW, St. Clair, IL

Built 1993 Load: 41.1 t ADT: 15,100

IL 159

Good

Over: Br of Canteen Creek

500 s of madison co, St. Clair, IL

Built 2012 Load: 41.1 t ADT: 16,100

IL 4

Good

Over: MUD CREEK

1.2 MI N JCT IL 13, St. Clair, IL

Built 1992 Load: 41.5 t ADT: 1,550

OLD IL 3 - FAU 929

Good

Over: HILL CREEK

1.1M S DUPO, St. Clair, IL

Built 1997 Load: 41.5 t ADT: 2,600

ILL 15 WB

Good

Over: RICHLAND CREEK

1.0 M E JCT ILL 159, St. Clair, IL

Built 1956 Load: 41.8 t ADT: 12,500

ILL 15 EB

Good

Over: RICHLAND CREEK

1.0 M E JCT ILL 159, St. Clair, IL

Built 1956 Load: 41.8 t ADT: 12,500

FAI 64 EB

Good

Over: ILL 157

CASEYVILLE, St. Clair, IL

Built 2007 Load: 41.8 t ADT: 41,500

FAI 64 WB

Good

Over: ILL 157

CASEYVILLE, St. Clair, IL

Built 2007 Load: 41.8 t ADT: 41,500

TR 120 Mulligan Ln

Good

Over: Br of Richland Cr

1.14 Mi W of IL 159, St. Clair, IL

Built 2020 Load: 41.8 t ADT: 125

EB I-70 Flyover Ra

Good

Over: I-55 64 Ramps KCSRR CSX

4th level of Quad-Level, St. Clair, IL

Built 2014 Load: 42.1 t ADT: 21,000

Bond Ave

Good

Over: A&SRR

39TH & BOND ALORTON, St. Clair, IL

Built 1980 Load: 42.4 t ADT: 3,250

1L 15

Good

Over: SILVER CREEK

2.5 MI E FREEBURG, St. Clair, IL

Built 1993 Load: 42.4 t ADT: 2,600

IL. 161

Good

Over: Trib to SHOENBRGR CR

.06 SO. ST. CLAIR AV, St. Clair, IL

Built 2000 Load: 42.4 t ADT: 13,500

IL 13 EB TO IL 15

Good

Over: TRIB TO RICHLAND CRK

1.6 M SE IL 158& 177, St. Clair, IL

Built 2006 Load: 42.4 t ADT: 450

POCKET RD/ FAU 923

Good

Over: FAI 255

S EDGE FHSP, St. Clair, IL

Built 1981 Load: 42.8 t ADT: 200

Rel. IL 3 (Packers

Good

Over: KCSRR Water St UPRR

0.6 mi W. of I-70, St. Clair, IL

Built 2016 Load: 42.8 t ADT: 2,350

ILL 203 NB

Good

Over: SB RAMP TO EB 55/70

0.6 M E E ST LOUIS, St. Clair, IL

Built 1960 Load: 43.1 t ADT: 7,600

IL 4

Good

Over: LITTLE SILVER CK

0.9 Mi S of US 50, St. Clair, IL

Built 1997 Load: 43.1 t ADT: 5,150

MISSOURI AV/FAU 91

Good

Over: I-55/64; US 40 WB

1/2 mi W 3RD ST EXIT, St. Clair, IL

Built 1965 Load: 43.4 t ADT: 10

FAI 255 SB

Good

Over: HARDING DITCH north

1.9MI N FAI 64, St. Clair, IL

Built 1985 Load: 43.4 t ADT: 21,750

MLK RAMP 1 EB

Good

Over: IL 3 TRRA UPRR MoAv 55-6

EAST APPROACH MLK, St. Clair, IL

Built 2000 Load: 43.4 t ADT: 1,750

IL 177

Good

Over: LOOP CREEK

3MI WEST OF 158, St. Clair, IL

Built 2007 Load: 43.4 t ADT: 7,800

N Main St / FAU 92

Good

Over: FAI 64

1/2 mi S of US 50, St. Clair, IL

Built 1972 Load: 43.7 t ADT: 5,300

IL 157

Good

Over: creek Metrolink St Clair

1.2 mi S. of I-64, St. Clair, IL

Built 2017 Load: 44.1 t ADT: 9,550

IL 13

Good

Over: E Trib to Doza Creek

0.9MI NW MARISSA, St. Clair, IL

Built 2014 Load: 44.1 t ADT: 3,350

EXCHANGE AVENUE

Good

Over: I-55/70

E ST L AT BOWMAN YD, St. Clair, IL

Built 2011 Load: 44.4 t ADT: 1,225

FAU 9181 SUMMIT AV

Good

Over: HARDING DITCH

0.7 M E JCT ILL 111, St. Clair, IL

Built 1957 Load: 44.7 t ADT: 1,900

ILL 15 WB

Good

Over: ILL 159

0.30MI S IL 158&177, St. Clair, IL

Built 1957 Load: 45.0 t ADT: 12,500

ILL 15 EB

Good

Over: ILL 159

0.32MI S IL 158&177, St. Clair, IL

Built 1957 Load: 45.0 t ADT: 20,500

RELOCATED I-70 EB

Good

Over: 1ST STREET in E St L

0.4 mi N of I-55/64, St. Clair, IL

Built 2013 Load: 45.0 t ADT: 21,000

I-70 WB

Good

Over: NSRR TRRA Industrial Ave

1.4 mi N of I-55/64, St. Clair, IL

Built 2013 Load: 45.0 t ADT: 22,150

N GREENMOUNT RD

Good

Over: FAI 64

.87 MI S OF US 50, St. Clair, IL

Built 2001 Load: 45.0 t ADT: 10,200

Rel. IL 3 (Packers

Good

Over: KCSRR Water St UPRR

0.6 mi W. of I-70, St. Clair, IL

Built 2016 Load: 45.7 t ADT: 2,350

IL 3

Good

Over: UPRR Prarie duPont Cana

NORTH OF DUPO, St. Clair, IL

Built 2012 Load: 46.0 t ADT: 9,600

ILL 15 WB

Good

Over: ILL 158

S BELLEVILLE, St. Clair, IL

Built 1958 Load: 46.0 t ADT: 21,500

ILL 15 EB

Good

Over: ILL 158

S BELLEVILLE, St. Clair, IL

Built 1958 Load: 46.0 t ADT: 20,500

ILL 13

Good

Over: ILL 15

SW BELLEVILLE, St. Clair, IL

Built 1959 Load: 46.0 t ADT: 7,350

RELOCATED I-70 WB

Good

Over: 1ST STREET in E ST L

0.4 mi N of I-55/64, St. Clair, IL

Built 2013 Load: 46.0 t ADT: 21,000

ILL 203

Good

Over: FAI 70

0.5 M N E ST LOUIS, St. Clair, IL

Built 1960 Load: 46.3 t

IL 161

Good

Over: Metrolink

0.1mi W of IL 159, St. Clair, IL

Built 1935 Load: 46.3 t ADT: 14,700

Rieder Road TR 222

Good

Over: FAI 64

1.64 MI E OF ILL 158, St. Clair, IL

Built 2017 Load: 46.3 t ADT: 1,550

IL 161 NORTHBOUND

Good

Over: SCHOENBERGER CREEK

1MI SO. ST CLAIR AVE, St. Clair, IL

Built 2007 Load: 46.7 t ADT: 14,800

IL 161 SOUTHBOUND

Good

Over: SCHOENBERGER CREEK

IMI SO. ST CLAIR AVE, St. Clair, IL

Built 2007 Load: 46.7 t ADT: 14,800

BUNKUM RD/ FAU 916

Good

Over: FAI 64

1.99 MI E ILL 157, St. Clair, IL

Built 1971 Load: 46.7 t ADT: 5,400

FAI 255

Good

Over: HILL CREEK

1.5 MI S OF DUPO, St. Clair, IL

Built 1979 Load: 46.7 t ADT: 41,000

MSS 6035

Good

Over: HILL CREEK

1.5 M SO OF DUPO, St. Clair, IL

Built 1979 Load: 46.7 t ADT: 125

15TH ST-FAU 9155

Good

Over: FAI 64 in E ST Louis

0.79 E OF FAI 70, St. Clair, IL

Built 2012 Load: 47.0 t ADT: 1,150

Rel. IL 3 (Packers

Good

Over: St. Clair Ave TRRA

0.8 mi N of I-55/64, St. Clair, IL

Built 2013 Load: 47.3 t ADT: 3,050

TR 194 Reinneck Rd

Good

Over: Hazel Creek

0.25 Mi N Jefferson, St. Clair, IL

Built 2018 Load: 47.3 t ADT: 225

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.