Ranking · states and soil series
Where the US has expansive, shrink-swell clay soil
Among the 1,509 most widespread soils in the country, 47 are Vertisols, the clays that swell when wet and shrink and crack when dry. Together they cover 26 million acres. Texas has the most, with 9.9 million acres.
- Vertisol series
- 47
- among the most widespread soils
- Mapped acres
- 26 million
- acres
- Top state
- 9.9 million
- acres · Texas
States with the most shrink-swell clay
Acres of Vertisols
| State | Acres of Vertisols | Share of state |
|---|---|---|
| 1. Texas | 9,913,928 | 5.9% |
| 2. South Dakota | 3,148,170 | 6.3% |
| 3. Louisiana | 2,753,676 | 10.1% |
| 4. Arkansas | 1,817,454 | 5.5% |
| 5. Mississippi | 1,736,098 | 6.1% |
| 6. Montana | 1,455,230 | 1.5% |
| 7. North Dakota | 918,245 | 2.1% |
| 8. California | 808,526 | 0.8% |
| 9. Oklahoma | 727,957 | 1.7% |
| 10. Missouri | 520,067 | 1.2% |
| 11. Arizona | 469,078 | 0.6% |
| 12. Minnesota | 450,914 | 0.9% |
Shrink-swell soils to know by name
Largest Vertisol series
| Soil series | Acres | Mostly in |
|---|---|---|
| 1. Sharkey | 3,645,880 | Louisiana, Arkansas, Mississippi |
| 2. Houston Black | 1,411,597 | Texas |
| 3. Alligator | 1,183,504 | Mississippi, Arkansas, Louisiana |
| 4. Heiden | 1,099,293 | Texas, Oklahoma |
| 5. Opal | 1,052,750 | South Dakota, Nebraska |
| 6. Fargo | 977,649 | North Dakota, Minnesota, Montana |
| 7. Perry | 911,415 | Arkansas, Louisiana, Texas |
| 8. Promise | 844,657 | South Dakota, Montana, Nebraska |
| 9. Victoria | 730,829 | Texas |
| 10. Lake Charles | 657,410 | Texas |
| 11. Millboro | 547,081 | South Dakota, Nebraska |
| 12. Montell | 531,153 | Texas |
| 13. Marvan | 527,677 | Montana, Wyoming |
| 14. Kyle | 505,515 | South Dakota, Montana, Nebraska |
| 15. Bascovy | 501,826 | Montana |
Why builders worry about these soils
Vertisols are rich in clay minerals such as smectite that soak up water between their layers. A wet Vertisol can swell enough to lift a slab foundation, and a dry one opens cracks wide enough to put a hand in. The repeated movement cracks foundations, buckles sidewalks and breaks pipes, which is why builders in expansive-clay regions often use foundations designed for it.
Vertisols are not the only expansive soils, so a clay soil without the name can still move. For a house, a geotechnical report on the lot is what decides the foundation design. Keeping soil moisture steady around a foundation (gutters that drain away, steady watering in drought) reduces movement.
Sources & data dates
- Source
- USDA NRCS Soil Survey Geographic Database (SSURGO), queried through Soil Data Access. Public domain.
- Data date
- SSURGO as published on November 3, 2026 (most recent survey area update October 26, 2026). NRCS refreshes SSURGO each October.
- Scope
- All mapped land in the 50 states and DC in the current soil survey.
- Method
- Covers the 1,509 named series with detailed records on this site (the 1,000 largest, each above about 330,000 acres, plus every series with a page), so state totals are a floor: smaller Vertisol series add more. Soil order is from USDA Soil Taxonomy. Full methodology.