County profile · official public datasets

Marlboro County, SC

96 public highway bridges tracked in the FHWA National Bridge Inventory: 40.6% rated Good, 53.1% Fair, 6.3% Poor.

96
Public bridges: 40.6%
Good condition: 6.3%
Poor condition

The verdict

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

Marlboro 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.

28th
of 46 on Poor share: 6.3%
Poor-condition share: 96
public highway bridges: 1971
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.

Marlboro County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Marlboro County ranks #28 of 46 South Carolina counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.3%). Marlboro County, South Carolina contains 96 public highway bridges. Roughly 40.6% are rated “Good,” 53.1% “Fair,” and 6.3% “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

Public highway bridges in Marlboro County

Good condition

40.6%

39 of 96 rated 7-9

Fair condition

53.1%

51 of 96 rated 5-6

Poor condition

6.3%

6 of 96 rated 4 or below

In-state Poor-share rank

#28 of 46

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

Condition distribution

Share of 96 NBI-tracked bridges by lowest applicable component rating.

Good

40.6% (39)

Fair

53.1% (51)

Poor

6.3% (6)

Marlboro County's Poor-condition bridges carry 26,225 vehicle crossings a day

That is 12.5% of the county's reported daily bridge traffic on 6.3% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 4,371 crossings a day against 2,080 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 96 of 96 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

56.3% of Marlboro County's bridges have passed the 50-year mark

54 of the 96 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 40.6% 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 36.6% of the county's Poor-condition bridge traffic

SC 9 BUS over CROOKED CREEK, built 1921, carries 9,600 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 6-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 26,225 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1920s

5
1930s

22
1950s

2
1960s

21
1970s

6
1980s

6
1990s

11
2000s

18
2010s

5

What this shows Construction peaked in the 1930s, when 22 of the county's bridges still in the inventory were built, which is 22.9% of those with a recorded year. That cohort is now 85 to 94 years old in the 2024 inventory. Its average build year is 1971, 6 years older than the South Carolina average of 1977.

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

The 5 South Carolina counties nearest Marlboro County in number of bridges, with their condition splits. Its 6.3% Poor share is the 5th-lowest of these 6. Its average build year of 1971 against a peer-group mean of 1975 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 Marlboro County and the 5 South Carolina counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Georgetown County	113	33.6%	61.1%	5.3%	1977
Hampton County	113	25.7%	68.1%	6.2%	1972
Marion County	112	34.8%	60.7%	4.5%	1974
Marlboro County (this page)	96	40.6%	53.1%	6.3%	1971
Lee County	91	46.2%	51.6%	2.2%	1983
Bamberg County	80	20%	67.5%	12.5%	1971

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

Similar inventory size

Nearest county inventories outside SC (96 bridges here).

Del Norte County, CA · 96 bridges
Routt County, CO · 96 bridges
Blaine County, ID · 96 bridges
Clare County, MI · 96 bridges

Similar average build year

Nearest mean year-built outside SC (1971 here).

Wayne County, MI · avg 1971 · 1,026 bridges
Baltimore County, MD · avg 1971 · 783 bridges
Washington County, PA · avg 1971 · 655 bridges
Linn County, OR · avg 1971 · 566 bridges

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

All 96 Good 39 Fair 51 Poor 6

All bridges (96)

Sort:

SC 9 NB

Fair

Over: S.C.L. RAILROAD

1MI E OF WALLACE, Marlboro, SC

Marlboro County Bridge Snapshot

Condition distribution

Marlboro County's Poor-condition bridges carry 26,225 vehicle crossings a day

56.3% of Marlboro County's bridges have passed the 50-year mark

One structure carries 36.6% of the county's Poor-condition bridge traffic

How Marlboro 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

All bridges (96)

SC 9 NB

US 15

SC 9

SC 9

S-35-381

S-35-381

SC 177

SC 79

S-35-220

S-35-32

US 15

US 15

SC 381

US 15

US 15

US 15

S-35-43

SC 381

SC 912

SC 38 WB

S-35-36

S-35-63

SC 912

SC 385

SC 38 EB

SC 38 EB

SC 38 WB

SC 34

SC 34

S-35-34

SC 34

S-35-34

SC 381

US 1

S-35-37

S-35-26

S-35-261

S-35-71

S-35-55

S-35-33

SC 9 BUS

US 15

S-609

S-35-36

SC 83

SC 9

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