Total bridges
49
Public highway bridges in Corson County
County profile · official public datasets
Corson County, SD
49 public highway bridges tracked in the FHWA National Bridge Inventory: 32.7% rated Good, 57.1% Fair, 10.2% Poor.
- 49
- Public bridges
- 32.7%
- Good condition
- 10.2%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Corson County posts a better-than-median Poor-condition share among rated counties in the state across rated county bridge inventory.
- Top 35%
- lowest Poor share in state
- 10.2%
- Poor-condition share
- 49
- 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.
Corson County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Corson County ranks #23 of 66 South Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 10.2%). Corson County, South Dakota contains 49 public highway bridges. Roughly 32.7% are rated “Good,” 57.1% “Fair,” and 10.2% “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.
Good condition
32.7%
16 of 49 rated 7-9
Fair condition
57.1%
28 of 49 rated 5-6
Poor condition
10.2%
5 of 49 rated 4 or below
In-state Poor-share rank
#23 of 66
Among South Dakota counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 49 NBI-tracked bridges by lowest applicable component rating.
Good 32.7% (16)
Fair 57.1% (28)
Poor 10.2% (5)
Corson County's Poor-condition bridges carry 2,990 vehicle crossings a day
That is 17.2% of the county's reported daily bridge traffic on 10.2% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 598 crossings a day against 223 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 49 of 49 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
59.2% of Corson County's bridges have passed the 50-year mark
29 of the 49 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 32.7% 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 46.6% of the county's Poor-condition bridge traffic
IRR US012 over CLAYMORE CK, built 1958, carries 1,392 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 5-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 2,990 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Corson County's bridges were built
49 bridges with a recorded construction year, grouped by decade
- 1930s 5
1930–1939
5 bridges
- 1940s 1
1940–1949
1 bridges
- 1950s 3
1950–1959
3 bridges
- 1960s
1960–1969
16 bridges
- 1970s 6
1970–1979
6 bridges
- 1980s 5
1980–1989
5 bridges
- 1990s 4
1990–1999
4 bridges
- 2000s 6
2000–2009
6 bridges
- 2010s 3
2010–2019
3 bridges
What this shows Construction peaked in the 1960s, when 16 of the county's bridges still in the inventory were built, which is 32.7% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1973) matches the South Dakota average (1975).
How Corson County compares with South Dakota's closest counties by inventory size
The 5 South Dakota counties nearest Corson County in number of bridges, with their condition splits. Its 10.2% Poor share is the 3rd-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.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Sanborn County | 53 | 34% | 49.1% | 17% | 1974 |
| Gregory County | 51 | 39.2% | 54.9% | 5.9% | 1976 |
| Harding County | 49 | 51% | 46.9% | 2% | 1985 |
| Corson County (this page) | 49 | 32.7% | 57.1% | 10.2% | 1973 |
| Faulk County | 46 | 19.6% | 58.7% | 21.7% | 1966 |
| Douglas County | 44 | 45.5% | 38.6% | 15.9% | 1969 |
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 Corson 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 Corson County, both outside South Dakota so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside SD (49 bridges here).
- Mono County, CA · 49 bridges
- Yuma County, CO · 49 bridges
- Calhoun County, FL · 49 bridges
- Crawford County, GA · 49 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.
Good-condition bridges (16)
211th Avenue
GoodOver: BLACK HORSE BUTTE CK
4E & 27S THUNDER HAWK, Corson, SD
Built 1999 Load: 24.5 t ADT: 30
IRR SD073
GoodOver: BURLINGTON NORTHERN RR
0.1 S NORTH DAKOTA LINE, Corson, SD
Built 1977 Load: 29.9 t ADT: 295
107th Street
GoodOver: Oak Creek
1.0W & 2.0N MCLAUGHLIN, Corson, SD
Built 2005 Load: 30.1 t ADT: 25
IRR BIA RTE 21
GoodOver: ROCK CREEK
IN BULLHEAD SOUTH DAKOTA, Corson, SD
Built 1971 Load: 32.6 t ADT: 203
IRR BIA RTE 4
GoodOver: FIRE STEEL CREEK
8 KM EAST OF HWY 65, Corson, SD
Built 1987 Load: 36.5 t ADT: 45
IRR BIA RTE 4
GoodOver: LITTLE OAK CREEK
5.8KM SW OF LITTLE EAGLE, Corson, SD
Built 2002 Load: 37.7 t ADT: 116
IRR BIA RTE 4
GoodOver: HIGHBANK CREEK BRIDGE
8.93KM SW OF LITTLE EAGLE, Corson, SD
Built 2008 Load: 37.7 t ADT: 109
IRR SD065
GoodOver: GRAND RV
15 N DEWEY CO LINE, Corson, SD
Built 2012 Load: 38.2 t ADT: 244
IRR BIA RTE 44
GoodOver: OAK CREEK
7.2 KM SE OF MAHTO, Corson, SD
Built 2010 Load: 38.5 t ADT: 100
Twin Butte Road
GoodOver: Trib. to Blk Horse Butte
1.0W & 28.5S KELDRON, Corson, SD
Built 2005 Load: 45.9 t ADT: 14
IRR SD063
GoodOver: CK
0.9 N OF MCLAUGHLIN, Corson, SD
Built 1980 Load: 57.5 t ADT: 875
IRR SD020
GoodOver: CK
8.3 W OF TRAIL CITY, Corson, SD
Built 2000 Load: 84.3 t ADT: 1,031
IRR US012
GoodOver: CK
2.0 W JCT SD 63, Corson, SD
Built 1991 Load: 84.6 t ADT: 402
Twin Butte Road
GoodOver: Grand River
9E & 18S THUNDER HAWK, Corson, SD
Built 1990 Load: 99.9 t ADT: 20
237TH AVENUE
GoodOver: FIRESTEEL CREEK
3E & 6.7N ISABEL, Corson, SD
Built 2007 Load: 99.9 t ADT: 30
WEST BULLHEAD ROAD
GoodOver: WHITE SHIRT CREEK
2.4E & 9.7S MCINTOSH, Corson, SD
Built 2016 Load: 99.9 t ADT: 30
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.