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

All bridges (486)

ILL 177

Good

Over: ASH CREEK

0.7 MI E ILL 158, St. Clair, IL

Built 1991 Load: 33.4 t ADT: 7,150

ILL 177

Good

Over: E Trib Reinhardt SL

1.8M E JCT IL 4, St. Clair, IL

Built 1994 Load: 33.4 t ADT: 2,450

IL 159

Good

Over: Trib to Richland Crk

3.2 MI N SMITHON, St. Clair, IL

Built 2001 Load: 33.4 t ADT: 8,100

FAU 9175

Good

Over: ROCK SPRING BRANCH

0.5M N US 50, St. Clair, IL

Built 1972 Load: 33.4 t ADT: 11,400

STATE STREET RD

Good

Over: CREEK

BELV S 1.5M IL 15, St. Clair, IL

Built 1999 Load: 33.4 t ADT: 1,700

US 50

Good

Over: SILVER CREEK

1.5 M W ILL 4, St. Clair, IL

Built 1939 Load: 33.7 t ADT: 16,000

I-64WB Ramp to 18

Good

Over: NSRR

0.4 mi W of 25th St., St. Clair, IL

Built 1974 Load: 34.0 t ADT: 37,900

I-255 NB

Good

Over: St. Clair Ave & Metrolin

0.50 mi N of State St, St. Clair, IL

Built 1982 Load: 34.0 t ADT: 22,300

ILL 161

Good

Over: RICHLAND CREEK

.5 MI E ILL 159, St. Clair, IL

Built 1987 Load: 34.0 t ADT: 19,600

I-255 SB

Good

Over: Black Lane CSXRR CSXRR

1.2 mi S of I-55/70, St. Clair, IL

Built 1985 Load: 34.3 t ADT: 21,750

FAI 70A

Good

Over: MISSISSIPPI RIVER

RIVER CROSSING MAIN, St. Clair, IL

Built 2014 Load: 34.8 t ADT: 44,300

I-55/64EB mainlne"

Good

Over: UPRR IL 3 ramp UPRR UPRR

PIER BC1 TO ABUT C31, St. Clair, IL

Built 1967 Load: 35.0 t ADT: 58,850

IL 13

Good

Over: TRIB TO KASKASKIA RV

2.2M N NEW ATHENS, St. Clair, IL

Built 1996 Load: 35.3 t ADT: 5,450

SUMMRFIELD Rd-FAS8

Good

Over: FAI-64

3 M E ILL 4, St. Clair, IL

Built 1967 Load: 35.6 t ADT: 575

Ramp to IL 13 EB

Good

Over: ILL 15 WB

SW BELLEVILLE, St. Clair, IL

Built 1957 Load: 36.0 t ADT: 6,050

I-55/64WB mainlne"

Good

Over: UPRR IL 3 Ramp UPRR UPRR

PIER BC1-> ABUT B31, St. Clair, IL

Built 1967 Load: 36.0 t ADT: 29,050

OLD LINCOLN TRAIL

Good

Over: HOLLOW CREEK

.1 MI E ILL 161, St. Clair, IL

Built 1977 Load: 36.0 t ADT: 2,600

IL 15 - FA 817

Good

Over: TRIB OF L MUD CREEK

0.5 NW OF ST. LIBORY, St. Clair, IL

Built 1990 Load: 36.0 t ADT: 3,450

Scott Drive NB

Good

Over: ASH CREEK

0.4 M N JCT ILL 161, St. Clair, IL

Built 1952 Load: 36.3 t ADT: 3,700

Scott Drive SB

Good

Over: ASH CREEK

0.4 M N JCT ILL 161, St. Clair, IL

Built 1952 Load: 36.3 t ADT: 3,700

IL 158 SB

Good

Over: Trail NSRR Metrolink Rd

0.5 mi W of Scott AFB, St. Clair, IL

Built 1972 Load: 36.3 t ADT: 9,150

FAI 64 WB

Good

Over: Abandoned Rdwy C

0.12 E OF 18TH ST, St. Clair, IL

Built 1968 Load: 36.6 t ADT: 37,900

IL 4

Good

Over: Trib to Silver Creek

1/2 mi south of I-64, St. Clair, IL

Built 1995 Load: 36.6 t ADT: 7,800

FRANK SCOTT PKWY W

Good

Over: ILL 15

1.5 M E JCT 13, St. Clair, IL

Built 1964 Load: 36.9 t ADT: 7,800

FAI 64 EB

Good

Over: Abandoned Roadway C

0.13 E OF 18TH ST, St. Clair, IL

Built 1974 Load: 36.9 t ADT: 37,900

LAKE DR/ FAU 9185

Good

Over: FAI 255/HARDING DTCH

.3 MI E IL 111, St. Clair, IL

Built 1981 Load: 36.9 t ADT: 3,750

BUNKUM RD/ FAU 916

Good

Over: FAI 255

0.2MI N OF FAI 64, St. Clair, IL

Built 1985 Load: 36.9 t ADT: 1,500

FOREST BLVD/FAU 91

Good

Over: FAI 255/HARDING DITH

1.4MI N FAI 64, St. Clair, IL

Built 1985 Load: 36.9 t ADT: 550

I-70 EB

Good

Over: NSRR TRRA Industrial Ave

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

Built 2013 Load: 36.9 t ADT: 22,150

ILL 15

Good

Over: ILL 157

1.8 M E JCT ILL 163, St. Clair, IL

Built 1940 Load: 37.3 t ADT: 28,800

ILL 157

Good

Over: CANTEEN CREEK

N C LMTS CASEYVILLE, St. Clair, IL

Built 1990 Load: 37.9 t ADT: 11,300

IL 161 NB

Good

Over: DutchHollow Metrolink cr

2.2 mi SE of IL 157, St. Clair, IL

Built 1992 Load: 37.9 t ADT: 14,800

IL 161 SB

Good

Over: DutchHollow Metrolink cr

2.2mi SE of IL 157, St. Clair, IL

Built 1992 Load: 37.9 t ADT: 14,800

IL 158 NB

Good

Over: Trail NSRR Metrolink Rd

0.5 mi W of Scott AFB, St. Clair, IL

Built 2001 Load: 37.9 t ADT: 9,150

DAVIS ST/ FAU 9301

Good

Over: FISH LAKE

1.25MI W ILL RTE 3, St. Clair, IL

Built 1974 Load: 37.9 t ADT: 400

MLK Bridge E Appr.

Good

Over: IL3 TRRA(UPRR) 1st MO Av

0.75 E Mississippi River, St. Clair, IL

Built 2018 Load: 38.2 t ADT: 5,350

ILL 159

Good

Over: BR RICHLAND CREEK

under IL 15 bridges, St. Clair, IL

Built 1967 Load: 38.6 t ADT: 14,200

I-70 WB

Good

Over: KCSRR CSXRR

QuadLevel 55/70WB to 70WB, St. Clair, IL

Built 2014 Load: 38.9 t ADT: 21,000

ILL 13

Good

Over: POWDER MILL CREEK

1 M E CENTREVILLE, St. Clair, IL

Built 1929 Load: 39.5 t ADT: 3,250

IL 4

Good

Over: MUD CREEK OVERFLOW

0.56 MI N MARISSA, St. Clair, IL

Built 1992 Load: 39.5 t ADT: 1,550

IL 4

Good

Over: N Trib to Silver Crk

N Leg of IL 4/IL 161, St. Clair, IL

Built 1995 Load: 39.5 t ADT: 7,800

ILL 13 / IL 157

Good

Over: HARDING DITCH

SE OF JCT IL 163&157, St. Clair, IL

Built 1973 Load: 39.9 t ADT: 6,000

ILL 161

Good

Over: TRIB TO LOOP CREEK

1.22 M W OF ILL 158, St. Clair, IL

Built 1933 Load: 39.9 t ADT: 14,400

9TH STREET

Good

Over: FAI 64

East St. Louis, St. Clair, IL

Built 2013 Load: 40.2 t ADT: 1,600

BUNKUM RD/FAU 9160

Good

Over: HARDING DITCH

1 MI E IL 111, St. Clair, IL

Built 2008 Load: 40.5 t ADT: 1,500

WB 64 Ramp to WB 7

Good

Over: I-55/70 Ramps CSXRR KCSR

QuadLevel Flyover to 70WB, St. Clair, IL

Built 2014 Load: 40.8 t ADT: 14,100

IL 158

Good

Over: BR of Richland Creek

300 feet S of IL 15, St. Clair, IL

Built 2013 Load: 40.8 t ADT: 9,050

NORTH GREENMOUNT R

Good

Over: RICHLAND CREEK

1.5 MI N SHILOH RD, St. Clair, IL

Built 1987 Load: 40.8 t ADT: 19,200

FAI 255

Good

Over: SUMMIT AVE

0.3 MI N OF STATE ST, St. Clair, IL

Built 1982 Load: 41.1 t ADT: 44,600

ILL 159

Good

Over: RICHLAND CREEK

IN BELLEVILLE, St. Clair, IL

Built 1923 Load: 41.1 t ADT: 11,400

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.