Total bridges
103
Public highway bridges in Charles Mix County
County profile · official public datasets
Charles Mix County, SD
103 public highway bridges tracked in the FHWA National Bridge Inventory: 38.8% rated Good, 37.9% Fair, 23.3% Poor.
- 103
- Public bridges
- 38.8%
- Good condition
- 23.3%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Charles Mix County posts a higher-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.
- 50th
- of 66 on Poor share
- 23.3%
- Poor-condition share
- 103
- public highway bridges
- 1971
- 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.
Charles Mix County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Charles Mix County ranks #50 of 66 South Dakota counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 23.3%). Charles Mix County, South Dakota contains 103 public highway bridges. Roughly 38.8% are rated “Good,” 37.9% “Fair,” and 23.3% “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
38.8%
40 of 103 rated 7-9
Fair condition
37.9%
39 of 103 rated 5-6
Poor condition
23.3%
24 of 103 rated 4 or below
In-state Poor-share rank
#50 of 66
Among South Dakota counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 103 NBI-tracked bridges by lowest applicable component rating.
Good 38.8% (40)
Fair 37.9% (39)
Poor 23.3% (24)
Charles Mix County's Poor-condition bridges carry 1,229 vehicle crossings a day
That is 3.4% of the county's reported daily bridge traffic on 23.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 51 crossings a day against 526 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 103 of 103 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
57.3% of Charles Mix County's bridges have passed the 50-year mark
59 of the 103 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 38.8% 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 16.7% of the county's Poor-condition bridge traffic
30010 400th Avenue over Choteau Creek, built 1958, carries 205 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 24-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 1,229 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Charles Mix County's bridges were built
103 bridges with a recorded construction year, grouped by decade
- 1910s 1
1910–1919
1 bridges
- 1920s 4
1920–1929
4 bridges
- 1930s
1930–1939
12 bridges
- 1940s
1940–1949
14 bridges
- 1950s
1950–1959
7 bridges
- 1960s
1960–1969
12 bridges
- 1970s
1970–1979
14 bridges
- 1980s
1980–1989
8 bridges
- 1990s
1990–1999
9 bridges
- 2000s
2000–2009
11 bridges
- 2010s
2010–2019
8 bridges
- 2020s 3
2020–2029
3 bridges
What this shows Construction peaked in the 1940s, when 14 of the county's bridges still in the inventory were built, which is 13.6% of those with a recorded year. That cohort is now 75 to 84 years old in the 2024 inventory. Its average build year (1971) matches the South Dakota average (1975).
How Charles Mix County compares with South Dakota's closest counties by inventory size
The 5 South Dakota counties nearest Charles Mix County in number of bridges, with their condition splits. Its 23.3% Poor share is the 6th-lowest of these 6. Its average build year of 1971 against a peer-group mean of 1979 is 8 years older.
Showing the 5 closest of 65 South Dakota counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Lyman County | 114 | 40.4% | 50% | 9.6% | 1975 |
| Charles Mix County (this page) | 103 | 38.8% | 37.9% | 23.3% | 1971 |
| Yankton County | 99 | 41.4% | 43.4% | 15.2% | 1983 |
| McCook County | 98 | 44.9% | 44.9% | 10.2% | 1977 |
| Custer County | 95 | 46.3% | 48.4% | 5.3% | 1977 |
| Clay County | 94 | 58.5% | 25.5% | 16% | 1985 |
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 Charles Mix 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 Charles Mix County, both outside South Dakota so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside SD (103 bridges here).
- Kenai Peninsula County, AK · 103 bridges
- Dallas County, AR · 103 bridges
- Morgan County, GA · 103 bridges
- Rawlins County, KS · 103 bridges
Similar average build year
Nearest mean year-built outside SD (1971 here).
- Wayne County, MI · avg 1971 · 1,026 bridges
- Baltimore County, MD · avg 1971 · 783 bridges
- Washington County, PA · avg 1971 · 655 bridges
- Linn County, OR · avg 1971 · 566 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
All bridges (103)
39120 305th Street
PoorOver: Mosquito Creek
8.0S & 3.8W of Wagner, Charles Mix, SD
Built 1920 Load: 20.8 t ADT: 48
29120 383rd Avenue
PoorOver: Drainage Ditch
0.3N & 1.0E of Lake Andes, Charles Mix, SD
Built 1930 Load: 24.5 t ADT: 4
28870 385th Avenue
PoorOver: Creek
3.3N & 3.0E of Lake Andes, Charles Mix, SD
Built 1945 Load: 24.5 t ADT: 48
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.