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.

Total bridges

103

Public highway bridges in Charles Mix County

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.

1910s

1
1920s

4
1930s

12
1940s

14
1950s

7
1960s

12
1970s

14
1980s

8
1990s

9
2000s

11
2010s

8
2020s

3

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.

Bridge inventory size and condition shares for Charles Mix County and the 5 South Dakota counties closest to it in inventory size
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 103 Good 40 Fair 39 Poor 24

All bridges (103)

Sort:

Charles Mix County Bridge Snapshot

Condition distribution

Charles Mix County's Poor-condition bridges carry 1,229 vehicle crossings a day

57.3% of Charles Mix County's bridges have passed the 50-year mark

One structure carries 16.7% of the county's Poor-condition bridge traffic

How Charles Mix 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 (103)

38580 300th Street

39320 291st Street

37380 281st Street

30090 401st Avenue

29490 395th Avenue

35400 271st Street

270th Street

36590 274th Street

37000 271st Street

39360 294th Street

29660 395th Avenue

29640 396th Avenue

39960 300th Street

40120 302nd Street

303rd Street

40310 307th Street

28860 395th Avenue

39390 291st Street

36660 271st Street

27040 371st Avenue

375th Avenue

28960 395th Avenue

29090 395th Avenue

30040 401st Avenue

IRR SD050

Old IRR SD050

County Road 2

SD050

IRR US018

SD044

40260 312th Street

39370 295th Street

State Highway 281

IRR US018

37310 268th Street

SD044

SD050

SD045

IRR SD046

27680 364th Avenue

36650 273rd Street

39420 292nd Street

SD045

36460 275th Street

28490 376th Avenue

40430 306th Street

27380 366th Avenue

40130 305th Street

38560 303rd Street

SD050

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