County profile · official public datasets

Allendale County, SC

69 public highway bridges tracked in the FHWA National Bridge Inventory: 23.2% rated Good, 63.8% Fair, 13% Poor.

69
Public bridges: 23.2%
Good condition: 13%
Poor condition

The verdict

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

Allendale County pairs a higher-than-median Poor-condition share among rated counties in the state with an older average build year than the state inventory.

44th
of 46 on Poor share: 13%
Poor-condition share: 69
public highway bridges: 1968
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.

Allendale County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Allendale County ranks #44 of 46 South Carolina counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 13%). Allendale County, South Carolina contains 69 public highway bridges. Roughly 23.2% are rated “Good,” 63.8% “Fair,” and 13% “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

Public highway bridges in Allendale County

Good condition

23.2%

16 of 69 rated 7-9

Fair condition

63.8%

44 of 69 rated 5-6

Poor condition

13%

9 of 69 rated 4 or below

In-state Poor-share rank

#44 of 46

Among South Carolina counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 69 NBI-tracked bridges by lowest applicable component rating.

Good

23.2% (16)

Fair

63.8% (44)

Poor

13% (9)

Allendale County's Poor-condition bridges carry 4,350 vehicle crossings a day

That is 7.9% of the county's reported daily bridge traffic on 13% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 483 crossings a day against 323 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 69 of 69 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

63.8% of Allendale County's bridges have passed the 50-year mark

44 of the 69 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 23.2% 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 31% of the county's Poor-condition bridge traffic

US 301 over SAVANNAH RIVER, built 1965, carries 1,350 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 9-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 4,350 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1920s

5
1930s

3
1940s

6
1950s

11
1960s

14
1970s

13
1980s

1
1990s

8
2000s

4
2010s

4

What this shows Construction peaked in the 1960s, when 14 of the county's bridges still in the inventory were built, which is 20.3% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year is 1968, 9 years older than the South Carolina average of 1977.

How Allendale County compares with South Carolina's closest counties by inventory size

The 5 South Carolina counties nearest Allendale County in number of bridges, with their condition splits. Its 13% Poor share is the 6th-lowest of these 6. Its average build year of 1968 against a peer-group mean of 1971 is in line with the group.

Showing the 5 closest of 45 South Carolina counties eligible for comparison.

Bridge inventory size and condition shares for Allendale County and the 5 South Carolina counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Bamberg County	80	20%	67.5%	12.5%	1971
Barnwell County	76	30.3%	65.8%	3.9%	1966
Beaufort County	72	36.1%	59.7%	4.2%	1988
Allendale County (this page)	69	23.2%	63.8%	13%	1968
McCormick County	68	42.6%	57.4%	0%	1972
Calhoun County	64	20.3%	73.4%	6.3%	1959

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 Allendale 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 Allendale County, both outside South Carolina so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside SC (69 bridges here).

Irwin County, GA · 69 bridges
Edwards County, KS · 69 bridges
Barry County, MI · 69 bridges
Maries County, MO · 69 bridges

Similar average build year

Nearest mean year-built outside SC (1968 here).

Montgomery County, PA · avg 1968 · 828 bridges
San Joaquin County, CA · avg 1968 · 644 bridges
Providence County, RI · avg 1968 · 476 bridges
Imperial County, CA · avg 1968 · 444 bridges

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

All 69 Good 16 Fair 44 Poor 9

Fair-condition bridges (44)

Sort:

Allendale County Bridge Snapshot

Condition distribution

Allendale County's Poor-condition bridges carry 4,350 vehicle crossings a day

63.8% of Allendale County's bridges have passed the 50-year mark

One structure carries 31% of the county's Poor-condition bridge traffic

How Allendale County compares with South Carolina's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Fair-condition bridges (44)

S-3-342

S-3-350

S-3-336

S-3-336

S-3-55

SC 3

S-3-162

S-3-41

S-3-88

S-3-39

S-3-65

S-3-345

S-3-17

SC 125

US 321

S-3-18

S-3-40

S-3-18

S-3-18

SC 3

S-3-470

S-3-48

S-3-23

S-3-472

SC 641

US 301

SC 125

SC 125

US 278

US 321

US 301

US 301

US 301

US 321

US 278

SC 125

US 301

US 301

US 278

S-3-69

S-3-289

US 301

S-3-47

SC 125

Related