County profile · official public datasets

Marshall County, SD

39 public highway bridges tracked in the FHWA National Bridge Inventory: 15.4% rated Good, 51.3% Fair, 33.3% Poor.

39
Public bridges: 15.4%
Good condition: 33.3%
Poor condition

The verdict

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

Marshall 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.

63rd
of 66 on Poor share: 33.3%
Poor-condition share: 39
public highway bridges: 1965
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.

Marshall County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Marshall County ranks #63 of 66 South Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 33.3%). Marshall County, South Dakota contains 39 public highway bridges. Roughly 15.4% are rated “Good,” 51.3% “Fair,” and 33.3% “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 Marshall County

Good condition

15.4%

6 of 39 rated 7-9

Fair condition

51.3%

20 of 39 rated 5-6

Poor condition

33.3%

13 of 39 rated 4 or below

In-state Poor-share rank

#63 of 66

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

Condition distribution

Share of 39 NBI-tracked bridges by lowest applicable component rating.

Good

15.4% (6)

Fair

51.3% (20)

Poor

33.3% (13)

Marshall County's Poor-condition bridges carry 782 vehicle crossings a day

That is 6.2% of the county's reported daily bridge traffic on 33.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 60 crossings a day against 274 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 39 of 39 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

61.5% of Marshall County's bridges have passed the 50-year mark

24 of the 39 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 15.4% 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 41.2% of the county's Poor-condition bridge traffic

415th Avenue over Crow Creek Ditch, built 1974, carries 322 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 13-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 782 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1920s

1
1930s

10
1940s

3
1950s

2
1960s

5
1970s

7
1980s

3
1990s

2
2000s

1
2010s

5

What this shows Construction peaked in the 1930s, when 10 of the county's bridges still in the inventory were built, which is 25.6% of those with a recorded year. That cohort is now 85 to 94 years old in the 2024 inventory. Its average build year is 1965, 10 years older than the South Dakota average of 1975.

How Marshall County compares with South Dakota's closest counties by inventory size

The 5 South Dakota counties nearest Marshall County in number of bridges, with their condition splits. Its 33.3% Poor share is the 6th-lowest of these 6. Its average build year of 1965 against a peer-group mean of 1969 is in line with the group.

Showing the 5 closest of 65 South Dakota counties eligible for comparison.

Bridge inventory size and condition shares for Marshall County and the 5 South Dakota counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Hughes County	40	40%	37.5%	22.5%	1978
Marshall County (this page)	39	15.4%	51.3%	33.3%	1965
Brule County	38	34.2%	63.2%	2.6%	1966
Jones County	37	13.5%	81.1%	5.4%	1965
Stanley County	37	37.8%	48.6%	13.5%	1969
Jerauld County	35	20%	54.3%	25.7%	1967

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

Similar inventory size

Nearest county inventories outside SD (39 bridges here).

Costilla County, CO · 39 bridges
Ouray County, CO · 39 bridges
Edmonson County, KY · 39 bridges
McCreary County, KY · 39 bridges

Similar average build year

Nearest mean year-built outside SD (1965 here).

Windsor County, VT · avg 1965 · 483 bridges
Bedford County, PA · avg 1965 · 417 bridges
Crawford County, PA · avg 1965 · 399 bridges
Harper County, KS · avg 1965 · 372 bridges

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

All 39 Good 6 Fair 20 Poor 13

All bridges (39)

Sort:

Marshall County Bridge Snapshot

Condition distribution

Marshall County's Poor-condition bridges carry 782 vehicle crossings a day

61.5% of Marshall County's bridges have passed the 50-year mark

One structure carries 41.2% of the county's Poor-condition bridge traffic

How Marshall County compares with South Dakota'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 (39)

11980 - 421 AVE

SD027

415th Avenue

114th Street

419th Avenue

420th Avenue

421st Avenue

SD010

SD025

SD027

SD027

SD010

SD027

SD027

SD027

419th Avenue

SD027

SD027

SD027

SD027

IRR SD010

446th Avenue

104th Street

415th Avenue

120th Street

420th Avenue

416th Avenue

113th Street

122nd Street

113th Street

427th Avenue

113th Street

425th Avenue

112th Street

118th Street

100th Street

422nd Avenue

418th Avenue

415th Avenue

Related