HomeSouth DakotaPennington County

Pennington County, South Dakota

Shrink-swell clay limits houses without basements on 52% of Pennington County's mapped land, a higher share than 92% of US counties. A shallow water table limits basements on 1%.

100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 22 flood losses here since 2016. 48% of homes were built before 1980, against 50% nationally; the median home dates from 1982.

Data as of October 13, 2026 · sources

52%

expansive clay: shrink-swell limits slab homes

1%

high water table: limits basements

100%

in drought, October 13, 2026

48%

of homes built before 1980

Soil under Pennington County

Expansive clay (limits slab homes)52.0%
High water table (limits basements)1.1%
Septic fields very limited88.1%
Clay swell (LEP, by area)6.7%
High-swell land (LEP 6%+)54.9%
Mapped soil1,787,482 acres
Soil seriesShare hereSeries nationally: expansive clay
Pierre9%n/a
Samsil8%n/a
Nunn8%n/a
Pactola7%n/a
Stovho4%n/a
Buska3%n/a
Custer County: 17%Meade County: 49%Oglala Lakota County: 23%Lawrence County: 22%Jackson County: 45%Fall River County: 55%Haakon County: 89%Butte County: 72%Pennington County CusterMeadeOglala LakotaLawrenceJacksonFall RiverHaakonButtePennington
Pennington 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 SD606 (2025-09-10), SD607 (2025-09-10)

What the numbers mean here

Clay swell averages a linear extensibility of 6.7% by land area here, and 55% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 52% of the mapped land.

Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 52% of Pennington County's mapped land has shrink-swell clay.

Rain over the 12 months to August 2026: 16.32 in, 3.02 in below the 1991-2020 average year of 19.34 in.

USDA rates 88% of the land very limited for septic absorption fields.

Drought

100% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 38 of the last 52 weeks; the most was 100% of its area, in 16 weeks, most recently on the October 13, 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 worse100%
D2 severe or worse3.9%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

22 flood losses since 2016, $233,984 paid. The worst year was 2019, with 14.

YearFlood losses
20160
20171
20185
201914
20200
20211
20220
20231
20240
20250
2026 to date0

Rain

Average year, 1991-202019.34 in
12 months to August 202616.32 in (-3.02)
202520.57 in (+1.23)
Wettest year since 18951915: 30.95 in
Driest year since 18951936: 9.44 in
Days with 1 inch or more, normal at RAPID CITY RGNL AP (12 mi away)2.4

Homes

Housing units51,681
Median year built1982
Built before 198048%
Built 2000 or later31%
Owner-occupied69%
Median value, owner-occupied$302,200
Single-family detached62%

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
Custer County, SD 38 mi 17% 1%
Meade County, SD 42 mi 49% 1%
Oglala Lakota County, SD 48 mi 23% 1%
Lawrence County, SD 54 mi 22% 1%
Jackson County, SD 64 mi 45% 2%
Fall River County, SD 64 mi 55% 1%
Haakon County, SD 67 mi 89% 6%
Butte County, SD 70 mi 72% 6%

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