County profile · official public datasets

LaSalle County, IL

528 public highway bridges tracked in the FHWA National Bridge Inventory: 39.4% rated Good, 48.3% Fair, 12.3% Poor.

528
Public bridges: 39.4%
Good condition: 12.3%
Poor condition

The verdict

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

LaSalle County posts a higher-than-median Poor-condition share among rated counties in the state across large county bridge inventory.

84th
of 102 on Poor share: 12.3%
Poor-condition share: 528
public highway bridges: 1978
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.

LaSalle County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, LaSalle County ranks #84 of 102 Illinois counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 12.3%). LaSalle County, Illinois contains 528 public highway bridges. Roughly 39.4% are rated “Good,” 48.3% “Fair,” and 12.3% “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

528

Public highway bridges in LaSalle County

Good condition

39.4%

208 of 528 rated 7-9

Fair condition

48.3%

255 of 528 rated 5-6

Poor condition

12.3%

65 of 528 rated 4 or below

In-state Poor-share rank

#84 of 102

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

Condition distribution

Share of 528 NBI-tracked bridges by lowest applicable component rating.

Good

39.4% (208)

Fair

48.3% (255)

Poor

12.3% (65)

LaSalle County's Poor-condition bridges carry 81,630 vehicle crossings a day

That is 7.5% of the county's reported daily bridge traffic on 12.2% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 1,275 crossings a day against 2,002 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 525 of 528 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

39% of LaSalle County's bridges have passed the 50-year mark

206 of the 528 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 39.4% 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 13.1% of the county's Poor-condition bridge traffic

US 6 FAP 623 over FOX RIVER, built 1928, carries 10,700 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 65-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 81,630 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

2
1910s

3
1920s

12
1930s

36
1940s

14
1950s

31
1960s

76
1970s

74
1980s

112
1990s

64
2000s

49
2010s

49
2020s

6

What this shows Construction peaked in the 1980s, when 112 of the county's bridges still in the inventory were built, which is 21.2% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year (1978) matches the Illinois average (1979).

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

The 5 Illinois counties nearest LaSalle County in number of bridges, with their condition splits. Its 12.3% Poor share is the 5th-lowest of these 6. Its average build year of 1978 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 LaSalle County and the 5 Illinois counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Livingston County	579	51.8%	39.9%	8.3%	1978
Iroquois County	570	46.5%	39.1%	14.4%	1980
LaSalle County (this page)	528	39.4%	48.3%	12.3%	1978
Madison County	523	49.3%	42.3%	8.4%	1979
Vermilion County	494	27.7%	65%	7.3%	1979
St. Clair County	486	50%	40.9%	9.1%	1977

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

Similar inventory size

Nearest county inventories outside IL (528 bridges here).

Merced County, CA · 528 bridges
Nueces County, TX · 528 bridges
New Castle County, DE · 527 bridges
Marathon County, WI · 530 bridges

Similar average build year

Nearest mean year-built outside IL (1978 here).

Orange County, CA · avg 1978 · 1,164 bridges
Sumner County, KS · avg 1978 · 659 bridges
Allen County, IN · avg 1978 · 613 bridges
Buncombe County, NC · avg 1978 · 555 bridges

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

All 528 Good 208 Fair 255 Poor 65

All bridges (528)

Sort:

LaSalle County Bridge Snapshot

Condition distribution

LaSalle County's Poor-condition bridges carry 81,630 vehicle crossings a day

39% of LaSalle County's bridges have passed the 50-year mark

One structure carries 13.1% of the county's Poor-condition bridge traffic

How LaSalle 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 (528)

CH 15

TR 382

FAS 268 B/CH 15

TR 19

CH-39

TR 205

TR 324 A

FAS268 A/CH 15

MORRIS RD (MS 2330

FAS268 B/CH15

I-39 SB/US 51 SB

TR-224

TWP RD TR 416

CH 29 /E.15TH RD

FAS 174N/CH 41

TR 7

TR 211

TR-3

TR 332-A

TR 402

TR 463

TR-456

CO RD 5

TR 523

FAS268 B/CH15

I-39 SB/US 51SB

I-39 NB/US 51 NB

ILL 71/FAP 311

FAS 174/CH 9

CO RD 42

TWP RD 170

CO RD 32

TR 87

TR-145

TR-157

TR 525

TR-437

TR 175

TWP RD TR 244

FAU 6087 SEVENTH S

ILL 71

FAS270 CH19

TR 282

TR-157

FAS 174N/CH 41

TR 441

TR 276

TR 4

TR 427

TR 205

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