HomeSouth DakotaCharles Mix County

Charles Mix County, South Dakota

Shrink-swell clay limits houses without basements on 29% of Charles Mix County's mapped land, a higher share than 80% of US counties. A shallow water table limits basements on 13%.

52.2% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 6 flood losses here since 2016. 63% of homes were built before 1980, against 50% nationally; the median home dates from 1971.

Data as of October 13, 2026 · sources

29%

expansive clay: shrink-swell limits slab homes

13%

high water table: limits basements

52%

in drought, October 13, 2026

63%

of homes built before 1980

Soil under Charles Mix County

Expansive clay (limits slab homes)29.1%
High water table (limits basements)12.8%
Septic fields very limited84.4%
Clay swell (LEP, by area)5.8%
High-swell land (LEP 6%+)29.5%
Mapped soil728,503 acres
Soil seriesShare hereSeries nationally: expansive clay
Highmore18%n/a
Eakin14%n/a
Ethan10%n/a
Mobridge5%n/a
Onita5%n/a
Tetonka4%n/a
Douglas County: 33%Boyd County: 52%Gregory County: 68%Aurora County: 42%Bon Homme County: 27%Davison County: 18%Hutchinson County: 21%Brule County: 43%Charles Mix County DouglasBoydGregoryAuroraBon HommeDavisonHutchinsonBruleCharles Mix
Charles Mix County (heavy outline) and nearby counties, shaded by expansive clay share.under 10%10-25%25-40%40-60%60%+

How we count · survey areas SD023 (2025-09-10)

What the numbers mean here

Clay swell averages a linear extensibility of 5.8% by land area here, and 30% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 29% of the mapped land.

Clay shrinks as it dries: 52.2% of the county is in drought on the latest map, and 29% of Charles Mix County's mapped land has shrink-swell clay.

Rain over the 12 months to August 2026: 18.30 in, 6.75 in below the 1991-2020 average year of 25.05 in.

USDA rates 84% of the land very limited for septic absorption fields.

Drought

52.2% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 52 of the last 52 weeks; the most was 100% of its area, in 28 weeks, most recently on the September 1, 2026 map.

October 21, 2025Share of area in drought, weeklyOctober 13, 2026
Category, October 13, 2026Share of county
D0 abnormally dry or worse100%
D1 moderate drought or worse52.2%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

6 flood losses since 2016, $193,030 paid. The worst year was 2019, with 4.

YearFlood losses
20161
20170
20180
20194
20200
20210
20220
20231
20240
20250
2026 to date0

Rain

Average year, 1991-202025.05 in
12 months to August 202618.30 in (-6.75)
202525.72 in (+0.67)
Wettest year since 18952019: 37.41 in
Driest year since 18951974: 14.01 in
Days with 1 inch or more, normal at PLATTE (18 mi away)5.1

Homes

Housing units3,668
Median year built1971
Built before 198063%
Built 2000 or later17%
Owner-occupied72%
Median value, owner-occupied$170,600
Single-family detached84%

What repairs cost

Published ranges from cost guides, not quotes. More sources, and where they disagree.

WorkRangeSource
Foundation repair, US $2,200 to $8,200 Fixr, January 27, 2026
Pier-and-beam repair, US $2,000 to $15,000 Fixr, January 27, 2026
Foundation inspection, US $300 to $600 Fixr, January 31, 2025

Nearby counties

PlaceDistanceExpansive clayHigh water table
Douglas County, SD 17 mi 33% 21%
Boyd County, NE 23 mi 52% 13%
Gregory County, SD 31 mi 68% 7%
Aurora County, SD 36 mi 42% 19%
Bon Homme County, SD 39 mi 27% 26%
Davison County, SD 40 mi 18% 20%
Hutchinson County, SD 43 mi 21% 25%
Brule County, SD 44 mi 43% 12%

Sources: USDA SSURGO (September 10, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status