Total bridges
170
Public highway bridges in Brown County
County profile · official public datasets
Brown County, SD
170 public highway bridges tracked in the FHWA National Bridge Inventory: 32.9% rated Good, 55.3% Fair, 11.8% Poor.
- 170
- Public bridges
- 32.9%
- Good condition
- 11.8%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Brown County pairs a better-than-median Poor-condition share among rated counties in the state with a newer average build year than the state inventory.
- Top 38%
- lowest Poor share in state
- 11.8%
- Poor-condition share
- 170
- public highway bridges
- 1983
- 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.
Brown County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Brown County ranks #25 of 66 South Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 11.8%). Brown County, South Dakota contains 170 public highway bridges. Roughly 32.9% are rated “Good,” 55.3% “Fair,” and 11.8% “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
32.9%
56 of 170 rated 7-9
Fair condition
55.3%
94 of 170 rated 5-6
Poor condition
11.8%
20 of 170 rated 4 or below
In-state Poor-share rank
#25 of 66
Among South Dakota counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 170 NBI-tracked bridges by lowest applicable component rating.
Good 32.9% (56)
Fair 55.3% (94)
Poor 11.8% (20)
Brown County's Poor-condition bridges carry 27,890 vehicle crossings a day
That is 18.7% of the county's reported daily bridge traffic on 11.8% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 1,395 crossings a day against 446 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 170 of 170 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
36.5% of Brown County's bridges have passed the 50-year mark
62 of the 170 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 32.9% 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 80.1% of the county's Poor-condition bridge traffic
US012 over MOCCASIN CK, built 1954, carries 22,327 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 20-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 27,890 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Brown County's bridges were built
170 bridges with a recorded construction year, grouped by decade
- 1900s 1
1900–1909
1 bridges
- 1910s 1
1910–1919
1 bridges
- 1920s 4
1920–1929
4 bridges
- 1930s
1930–1939
16 bridges
- 1940s 4
1940–1949
4 bridges
- 1950s
1950–1959
14 bridges
- 1960s 6
1960–1969
6 bridges
- 1970s
1970–1979
23 bridges
- 1980s
1980–1989
16 bridges
- 1990s
1990–1999
18 bridges
- 2000s
2000–2009
33 bridges
- 2010s
2010–2019
28 bridges
- 2020s 6
2020–2029
6 bridges
What this shows Construction peaked in the 2000s, when 33 of the county's bridges still in the inventory were built, which is 19.4% of those with a recorded year. That cohort is now 15 to 24 years old in the 2024 inventory. Its average build year is 1983, 8 years newer than the South Dakota average of 1975.
How Brown County compares with South Dakota's closest counties by inventory size
The 5 South Dakota counties nearest Brown County in number of bridges, with their condition splits. Its 11.8% Poor share is the 1st-lowest of these 6. Its average build year of 1983 against a peer-group mean of 1966 is 17 years newer.
Showing the 5 closest of 65 South Dakota counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Spink County | 176 | 13.6% | 52.8% | 33.5% | 1957 |
| Union County | 170 | 31.2% | 49.4% | 19.4% | 1975 |
| Brown County (this page) | 170 | 32.9% | 55.3% | 11.8% | 1983 |
| Hutchinson County | 161 | 32.9% | 50.9% | 16.1% | 1974 |
| Roberts County | 157 | 22.9% | 52.9% | 24.2% | 1970 |
| Beadle County | 152 | 19.1% | 47.4% | 33.6% | 1955 |
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 Brown 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 Brown County, both outside South Dakota so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside SD (170 bridges here).
- Rush County, KS · 170 bridges
- Itasca County, MN · 170 bridges
- Montgomery County, MS · 170 bridges
- Clarendon County, SC · 170 bridges
Similar average build year
Nearest mean year-built outside SD (1983 here).
- Dallas County, TX · avg 1983 · 3,230 bridges
- Bexar County, TX · avg 1983 · 2,342 bridges
- Sedgwick County, KS · avg 1983 · 1,333 bridges
- Will County, IL · avg 1983 · 649 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Good-condition bridges (56)
147TH STREET
GoodOver: Creek
1N & 0.1W VERDON, Brown, SD
Built 2015 Load: 73.8 t ADT: 98
406TH AVENUE
GoodOver: Creek
0.6N & 0.4E FERNEY, Brown, SD
Built 2015 Load: 73.8 t ADT: 98
407TH AVENUE
GoodOver: Creek
1E & 3.6S GROTON, Brown, SD
Built 2015 Load: 73.8 t ADT: 98
409TH AVENUE
GoodOver: Creek
1.9N & 3E GROTON, Brown, SD
Built 2015 Load: 73.8 t ADT: 37
112th Street
GoodOver: Willow Creek
10.8W & 2.0N of Barnard, Brown, SD
Built 2006 Load: 99.9 t ADT: 98
138th Street
GoodOver: Mud Creek
4N & 1.7W of Ferney, Brown, SD
Built 2012 Load: 99.9 t ADT: 56
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.