County profile · official public datasets

Pennington County, SD

348 public highway bridges tracked in the FHWA National Bridge Inventory: 30.2% rated Good, 62.4% Fair, 7.5% Poor.

348
Public bridges: 30.2%
Good condition: 7.5%
Poor condition

The verdict

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

Pennington County posts a top-quartile lowest Poor-condition share among rated counties in the state across mid-size county bridge inventory.

Top 24%
lowest Poor share in state: 7.5%
Poor-condition share: 348
public highway bridges: 1976
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.

Pennington County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Pennington County ranks #16 of 66 South Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 7.5%). Pennington County, South Dakota contains 348 public highway bridges. Roughly 30.2% are rated “Good,” 62.4% “Fair,” and 7.5% “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

348

Public highway bridges in Pennington County

Good condition

30.2%

105 of 348 rated 7-9

Fair condition

62.4%

217 of 348 rated 5-6

Poor condition

7.5%

26 of 348 rated 4 or below

In-state Poor-share rank

#16 of 66

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

Condition distribution

Share of 348 NBI-tracked bridges by lowest applicable component rating.

Good

30.2% (105)

Fair

62.4% (217)

Poor

7.5% (26)

Pennington County's Poor-condition bridges carry 12,863 vehicle crossings a day

That is 1.1% of the county's reported daily bridge traffic on 7.5% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 495 crossings a day against 3,274 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 347 of 348 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

62.9% of Pennington County's bridges have passed the 50-year mark

219 of the 348 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 30.2% 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 36.5% of the county's Poor-condition bridge traffic

CHAPEL LANE over RAPID CK, built 1974, carries 4,700 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 26-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 12,863 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

1
1920s

3
1930s

9
1940s

10
1950s

29
1960s

79
1970s

99
1980s

34
1990s

29
2000s

35
2010s

14
2020s

6

What this shows Construction peaked in the 1970s, when 99 of the county's bridges still in the inventory were built, which is 28.4% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1976) matches the South Dakota average (1975).

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

The 5 South Dakota counties nearest Pennington County in number of bridges, with their condition splits. Its 7.5% Poor share is the 1st-lowest of these 6. Its average build year of 1976 against a peer-group mean of 1978 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 Pennington County and the 5 South Dakota counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Minnehaha County	393	40.5%	50.1%	9.4%	1985
Pennington County (this page)	348	30.2%	62.4%	7.5%	1976
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	205	35.1%	48.8%	16.1%	1980

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

Similar inventory size

Nearest county inventories outside SD (348 bridges here).

Fillmore County, MN · 348 bridges
Cumberland County, NC · 348 bridges
Mahoning County, OH · 348 bridges
Cumberland County, PA · 348 bridges

Similar average build year

Nearest mean year-built outside SD (1976 here).

Marion County, IN · avg 1976 · 958 bridges
Mohave County, AZ · avg 1976 · 641 bridges
Comanche County, OK · avg 1976 · 593 bridges
Prince George's County, MD · avg 1976 · 576 bridges

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

All 348 Good 105 Fair 217 Poor 26

All bridges (348)

Sort:

Pennington County Bridge Snapshot

Condition distribution

Pennington County's Poor-condition bridges carry 12,863 vehicle crossings a day

62.9% of Pennington County's bridges have passed the 50-year mark

One structure carries 36.5% of the county's Poor-condition bridge traffic

How Pennington 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 (348)

E ASH ST

E OAK ST

E PINE ST

197TH AVE

SD044

MYSTIC ROAD

THUNDERHEAD FALLS

CROOKED CREEK RD

SD044

SD231

BIG FOOT RD

BIG FOOT RD

3RD STREET

TOWER DRIVE

160TH AVENUE

NEMO ROAD

SD040

ST PATRICK ST

SD044

FOREST ROAD

RESERVOIR ROAD

I90 WF (OFFETT ST)

ROCHFORD ROAD

DARK CANYON ROAD

MAPLE AVENUE

SAGE CREEK ROAD

151ST AVENUE

HISEGA DRIVE

SD044

SD044

CAMBELL ST

HISEGA DRIVE

LACROSSE ST

SD044

171 AVE

CHERRY AVENUE

MURPHY ROAD

32ND STREET

HISEGA DRIVE

NORRIS PEAK ROAD

SD231

CEDAR BUTTE RD

164 AVE

US016

DARK CANYON ROAD

DARK CANYON ROAD

TOWNSHIP RD

DARK CANYON ROAD

S. AIRPORT ROAD

SD244

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