HomeSouth DakotaOglala Lakota County
Oglala Lakota County, South Dakota
Shrink-swell clay limits houses without basements on 23% of Oglala Lakota County's mapped land, a higher share than 73% 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 no flood losses here since 2016. 42% of homes were built before 1980, against 50% nationally; the median home dates from 1987.
Data as of October 13, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, October 13, 2026
of homes built before 1980
Soil under Oglala Lakota County
| Expansive clay (limits slab homes) | 22.8% |
| High water table (limits basements) | 1.5% |
| Septic fields very limited | 82.3% |
| Clay swell (LEP, by area) | 4.8% |
| High-swell land (LEP 6%+) | 27.4% |
| Mapped soil | 1,450,983 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Canyon | 11% | n/a |
| Oglala | 8% | n/a |
| Keith | 6% | n/a |
| Interior | 5% | n/a |
| Pierre | 5% | n/a |
| Valentine | 5% | 0% |
How we count · survey areas SD612 (2025-09-10), SD613 (2025-09-10)
What the numbers mean here
Clay swell averages a linear extensibility of 4.8% by land area here, and 27% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 23% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 23% of Oglala Lakota County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 14.14 in, 5.11 in below the 1991-2020 average year of 19.25 in.
USDA rates 82% 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 36 of the last 52 weeks; the most was 100% of its area, in 34 weeks, most recently on the October 13, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 100% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
FEMA's flood data list no flood losses in Oglala Lakota County since 2016.
Rain
| Average year, 1991-2020 | 19.25 in |
| 12 months to August 2026 | 14.14 in (-5.11) |
| 2025 | 17.21 in (-2.04) |
| Wettest year since 1895 | 1915: 29.21 in |
| Driest year since 1895 | 1936: 10.64 in |
| Days with 1 inch or more, normal at PORCUPINE 11 N (10 mi away) | 3.5 |
Homes
| Housing units | 3,470 |
| Median year built | 1987 |
| Built before 1980 | 42% |
| Built 2000 or later | 21% |
| Owner-occupied | 52% |
| Median value, owner-occupied | $52,900 |
| Single-family detached | 69% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Bennett County, SD | 46 mi | 10% | 8% |
| Pennington County, SD | 48 mi | 52% | 1% |
| Fall River County, SD | 49 mi | 55% | 1% |
| Custer County, SD | 50 mi | 17% | 1% |
| Dawes County, NE | 52 mi | 24% | 1% |
| Jackson County, SD | 52 mi | 45% | 2% |
| Sheridan County, NE | 58 mi | 2% | 11% |
| Box Butte County, NE | 82 mi | 2% | 5% |
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