Musselshell County, Montana
Shrink-swell clay limits houses without basements on 24% of Musselshell County's mapped land, a higher share than 75% of US counties. A shallow water table limits basements on 1%.
None 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. 58% of homes were built before 1980, against 50% nationally; the median home dates from 1975.
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 Musselshell County
| Expansive clay (limits slab homes) | 24.0% |
| High water table (limits basements) | 0.8% |
| Septic fields very limited | 74.8% |
| Clay swell (LEP, by area) | 4.4% |
| High-swell land (LEP 6%+) | 24.3% |
| Mapped soil | 1,168,551 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Cabbart | 12% | under 1% |
| Delpoint | 11% | n/a |
| Cabba | 8% | n/a |
| Yamacall | 6% | n/a |
| Barvon | 5% | n/a |
| Neldore | 3% | n/a |
How we count · survey areas MT065 (2025-08-28)
What the numbers mean here
Clay swell averages a linear extensibility of 4.4% by land area here, and 24% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 24% of the mapped land.
Rain over the 12 months to August 2026: 14.40 in, 0.72 in below the 1991-2020 average year of 15.12 in.
USDA rates 75% of the land very limited for septic absorption fields.
Drought
0% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 33 of the last 52 weeks; the most was 100% of its area, in 20 weeks, most recently on the September 29, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 2.7% |
| D1 moderate drought or worse | 0% |
| 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 Musselshell County since 2016.
Rain
| Average year, 1991-2020 | 15.12 in |
| 12 months to August 2026 | 14.40 in (-0.72) |
| 2025 | 18.36 in (+3.24) |
| Wettest year since 1895 | 1978: 22.45 in |
| Driest year since 1895 | 1931: 5.98 in |
| Days with 1 inch or more, normal at ROUNDUP (6 mi away) | 1.4 |
Homes
| Housing units | 2,663 |
| Median year built | 1975 |
| Built before 1980 | 58% |
| Built 2000 or later | 22% |
| Owner-occupied | 85% |
| Median value, owner-occupied | $235,000 |
| Single-family detached | 78% |
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 |
|---|---|---|---|
| Golden Valley County, MT | 36 mi | 26% | 2% |
| Yellowstone County, MT | 40 mi | 23% | 3% |
| Petroleum County, MT | 45 mi | 57% | under 1% |
| Treasure County, MT | 59 mi | 44% | 4% |
| Fergus County, MT | 62 mi | 51% | 3% |
| Wheatland County, MT | 67 mi | n/a | n/a |
| Stillwater County, MT | 74 mi | 26% | 5% |
| Garfield County, MT | 86 mi | 22% | under 1% |
Sources: USDA SSURGO (August 28, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status