Marshall County, Illinois
A shallow water table limits basements on 66% of Marshall County's mapped land, a higher share than 78% of US counties. Shrink-swell clay limits houses without basements on 36%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 8 flood losses here since 2016. 77% of homes were built before 1980, against 50% nationally; the median home dates from 1961.
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 Marshall County
| Expansive clay (limits slab homes) | 36.3% |
| High water table (limits basements) | 65.6% |
| Septic fields very limited | 82.2% |
| Clay swell (LEP, by area) | 4.6% |
| High-swell land (LEP 6%+) | 18.3% |
| Mapped soil | 254,880 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Harco | 7% | n/a |
| Sable | 6% | n/a |
| Osco | 6% | 3% |
| Catlin | 6% | n/a |
| Rutland | 5% | n/a |
| Muscatune | 5% | n/a |
How we count · survey areas IL123 (2025-08-31)
What the numbers mean here
Clay swell averages a linear extensibility of 4.6% by land area here, and 18% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 36% of the mapped land.
On 66% of Marshall County's mapped land, soil stays saturated within about 6 feet of the surface for part of the year, which is basement depth.
Rain over the 12 months to August 2026: 35.52 in, 1.99 in below the 1991-2020 average year of 37.51 in.
USDA rates 82% 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 24 of the last 52 weeks; the most was 100% of its area, in 21 weeks, most recently on the March 31, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 0% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
8 flood losses since 2016, $101,800 paid. The worst year was 2017, with 3.
| Year | Flood losses |
|---|---|
| 2016 | 1 |
| 2017 | 3 |
| 2018 | 1 |
| 2019 | 1 |
| 2020 | 1 |
| 2021 | 1 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 37.51 in |
| 12 months to August 2026 | 35.52 in (-1.99) |
| 2025 | 30.20 in (-7.31) |
| Wettest year since 1895 | 1970: 53.08 in |
| Driest year since 1895 | 1956: 22.82 in |
| Days with 1 inch or more, normal at LACON (4 mi away) | 8.7 |
Homes
| Housing units | 5,815 |
| Median year built | 1961 |
| Built before 1980 | 77% |
| Built 2000 or later | 10% |
| Owner-occupied | 79% |
| Median value, owner-occupied | $142,800 |
| Single-family detached | 89% |
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 |
|---|---|---|---|
| Putnam County, IL | 12 mi | 23% | 50% |
| Woodford County, IL | 18 mi | 49% | 81% |
| Stark County, IL | 24 mi | 36% | 52% |
| Bureau County, IL | 27 mi | 25% | 53% |
| Peoria County, IL | 28 mi | 29% | 37% |
| LaSalle County, IL | 32 mi | 37% | 84% |
| Tazewell County, IL | 37 mi | 33% | 53% |
| Livingston County, IL | 42 mi | 53% | 96% |
Sources: USDA SSURGO (August 31, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status