County profile · official public datasets

Brookings County, SD

233 public highway bridges tracked in the FHWA National Bridge Inventory: 26.6% rated Good, 50.6% Fair, 22.7% Poor.

233
Public bridges: 26.6%
Good condition: 22.7%
Poor condition

The verdict

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

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

49th
of 66 on Poor share: 22.7%
Poor-condition share: 233
public highway bridges: 1973
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.

Brookings County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Brookings County ranks #49 of 66 South Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 22.7%). Brookings County, South Dakota contains 233 public highway bridges. Roughly 26.6% are rated “Good,” 50.6% “Fair,” and 22.7% “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

233

Public highway bridges in Brookings County

Good condition

26.6%

62 of 233 rated 7-9

Fair condition

50.6%

118 of 233 rated 5-6

Poor condition

22.7%

53 of 233 rated 4 or below

In-state Poor-share rank

#49 of 66

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

Condition distribution

Share of 233 NBI-tracked bridges by lowest applicable component rating.

Good

26.6% (62)

Fair

50.6% (118)

Poor

22.7% (53)

Brookings County's Poor-condition bridges carry 12,273 vehicle crossings a day

That is 3.9% of the county's reported daily bridge traffic on 22.7% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 232 crossings a day against 355 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 233 of 233 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

57.5% of Brookings County's bridges have passed the 50-year mark

134 of the 233 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 26.6% 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 11% of the county's Poor-condition bridge traffic

WESTERN AVE. over CK, built 1932, carries 1,356 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 53-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 12,273 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

2
1910s

3
1920s

4
1930s

25
1940s

6
1950s

18
1960s

34
1970s

59
1980s

13
1990s

18
2000s

34
2010s

10
2020s

7

What this shows Construction peaked in the 1970s, when 59 of the county's bridges still in the inventory were built, which is 25.3% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1973) matches the South Dakota average (1975).

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

The 5 South Dakota counties nearest Brookings County in number of bridges, with their condition splits. Its 22.7% Poor share is the 5th-lowest of these 6. Its average build year of 1973 against a peer-group mean of 1974 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 Brookings County and the 5 South Dakota counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Brookings County (this page)	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	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 Brookings 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 Brookings County, both outside South Dakota so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside SD (233 bridges here).

Pickens County, AL · 233 bridges
Washington County, IL · 233 bridges
Lawrence County, MO · 233 bridges
Oswego County, NY · 233 bridges

Similar average build year

Nearest mean year-built outside SD (1973 here).

Jefferson County, AL · avg 1973 · 1,068 bridges
Erie County, NY · avg 1973 · 906 bridges
Davidson County, TN · avg 1973 · 832 bridges
Lancaster County, PA · avg 1973 · 801 bridges

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

All 233 Good 62 Fair 118 Poor 53

All bridges (233)

Sort:

Brookings County Bridge Snapshot

Condition distribution

Brookings County's Poor-condition bridges carry 12,273 vehicle crossings a day

57.5% of Brookings County's bridges have passed the 50-year mark

One structure carries 11% of the county's Poor-condition bridge traffic

How Brookings 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 (233)

215TH STREET

475TH AVENUE

201ST STREET

470TH AVENUE

469TH AVENUE

206TH STREET

216TH STREET

216TH STREET

204TH STREET

212TH STREET

207TH STREET

216TH STREET

203RD STREET

212TH STREET

216TH STREET

478TH AVENUE

205TH STREET

465TH AVENUE

197TH STREET

197TH STREET

213TH STREET

213TH STREET

197TH STREET

214TH STREET

213TH STREET

469TH AVENUE

470TH AVENUE

473RD AVENUE

473RD AVENUE

473RD AVENUE

197TH STREET

201ST STREET

203 A STREET

478TH AVENUE

205TH STREET

479TH AVENUE

211TH STREET

480TH AVENUE

215TH STREET

485TH AVENUE

473RD AVENUE

485TH AVENUE

204TH STREET

I029

I029 S

I029 S

I029 N

I029 N

US014

US014

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