County profile · official public datasets

Grant County, SD

205 public highway bridges tracked in the FHWA National Bridge Inventory: 35.1% rated Good, 48.8% Fair, 16.1% Poor.

205
Public bridges: 35.1%
Good condition: 16.1%
Poor condition

The verdict

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

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

37th
of 66 on Poor share: 16.1%
Poor-condition share: 205
public highway bridges: 1980
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.

Grant County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Grant County ranks #37 of 66 South Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 16.1%). Grant County, South Dakota contains 205 public highway bridges. Roughly 35.1% are rated “Good,” 48.8% “Fair,” and 16.1% “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

205

Public highway bridges in Grant County

Good condition

35.1%

72 of 205 rated 7-9

Fair condition

48.8%

100 of 205 rated 5-6

Poor condition

16.1%

33 of 205 rated 4 or below

In-state Poor-share rank

#37 of 66

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

Condition distribution

Share of 205 NBI-tracked bridges by lowest applicable component rating.

Good

35.1% (72)

Fair

48.8% (100)

Poor

16.1% (33)

Grant County's Poor-condition bridges carry 4,665 vehicle crossings a day

That is 5.8% of the county's reported daily bridge traffic on 16.1% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 141 crossings a day against 338 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 205 of 205 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

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

80 of the 205 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 35.1% 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 54.9% of the county's Poor-condition bridge traffic

2nd Avenue over BN Railroad, built 1914, carries 2,560 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 33-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 4,665 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

4
1910s

1
1920s

9
1930s

25
1940s

10
1950s

14
1960s

13
1970s

14
1980s

6
1990s

16
2000s

52
2010s

26
2020s

15

What this shows Construction peaked in the 2000s, when 52 of the county's bridges still in the inventory were built, which is 25.4% of those with a recorded year. That cohort is now 15 to 24 years old in the 2024 inventory. Its average build year is 1980, 5 years newer than the South Dakota average of 1975.

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

The 5 South Dakota counties nearest Grant County in number of bridges, with their condition splits. Its 16.1% Poor share is the 3rd-lowest of these 6. Its average build year of 1980 against a peer-group mean of 1973 is 7 years newer.

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

Bridge inventory size and condition shares for Grant County and the 5 South Dakota counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Brookings County	233	26.6%	50.6%	22.7%	1973
Meade County	215	43.7%	45.6%	10.7%	1979
Lincoln County	207	34.3%	48.3%	17.4%	1973
Grant County (this page)	205	35.1%	48.8%	16.1%	1980
Spink County	176	13.6%	52.8%	33.5%	1957
Brown County	170	32.9%	55.3%	11.8%	1983

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

Similar inventory size

Nearest county inventories outside SD (205 bridges here).

Geneva County, AL · 205 bridges
Russell County, AL · 205 bridges
Wilson County, KS · 205 bridges
Bell County, KY · 205 bridges

Similar average build year

Nearest mean year-built outside SD (1980 here).

Tulsa County, OK · avg 1980 · 1,135 bridges
Miami-Dade County, FL · avg 1980 · 1,057 bridges
Pulaski County, AR · avg 1980 · 721 bridges
McLennan County, TX · avg 1980 · 714 bridges

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

All 205 Good 72 Fair 100 Poor 33

Fair-condition bridges (100)

Sort:

Grant County Bridge Snapshot

Condition distribution

Grant County's Poor-condition bridges carry 4,665 vehicle crossings a day

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

One structure carries 54.9% of the county's Poor-condition bridge traffic

How Grant 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

Fair-condition bridges (100)

SD020

SD015

154 STREET

452 AVENUE

452 AVE

452 AVE

145 ST

150 STREET

468 AVENUE

143 STREET

473 AVENUE

474 AVENUE

475TH AVENUE

155 STREET

153 STREET

477 AVENUE

477 AVENUE

477 AVENUE

477 AVE

479 AVENUE

148 STREET

147 ST

485 AVENUE

153 STREET

SD158

SD015

468 AVENUE

SD020

145 STREET

IRR I029 S

IRR I029 N

I029 S

I029 N

SD109

479 AVENUE

IRR I029 S

US012

US012

SD015

154 STREET

IRR I029

470 AVE

480 AVENUE

470 AVENUE

US012

SD123

US012

SD158

SD123

US012

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