Macoupin County, Illinois
A shallow water table limits basements on 78% of Macoupin County's mapped land, a higher share than 87% of US counties. Shrink-swell clay limits houses without basements on 62%.
42.2% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 1 flood losses here since 2016. 68% of homes were built before 1980, against 50% nationally; the median home dates from 1966.
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 Macoupin County
| Expansive clay (limits slab homes) | 61.6% |
| High water table (limits basements) | 78.3% |
| Septic fields very limited | 88.9% |
| Clay swell (LEP, by area) | 5.5% |
| High-swell land (LEP 6%+) | 57.8% |
| Mapped soil | 555,250 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Herrick | 14% | n/a |
| Hickory | 14% | n/a |
| Virden | 13% | n/a |
| Ipava | 5% | 100% |
| Rozetta | 5% | n/a |
| Marine | 5% | n/a |
How we count · survey areas IL117 (2025-08-31)
What the numbers mean here
Clay swell averages a linear extensibility of 5.5% by land area here, and 58% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 62% of the mapped land.
Clay shrinks as it dries: 42.2% of the county is in drought on the latest map, and 62% of Macoupin County's mapped land has shrink-swell clay.
On 78% of Macoupin 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: 36.55 in, 3.89 in below the 1991-2020 average year of 40.44 in.
USDA rates 89% of the land very limited for septic absorption fields.
Drought
42.2% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 27 of the last 52 weeks; the most was 100% of its area, in 16 weeks, most recently on the March 3, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 42.2% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
1 flood losses since 2016, $21,626 paid. The worst year was 2016, with 1.
| Year | Flood losses |
|---|---|
| 2016 | 1 |
| 2017 | 0 |
| 2018 | 0 |
| 2019 | 0 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 40.44 in |
| 12 months to August 2026 | 36.55 in (-3.89) |
| 2025 | 32.74 in (-7.70) |
| Wettest year since 1895 | 2008: 55.59 in |
| Driest year since 1895 | 1976: 25.15 in |
| Days with 1 inch or more, normal at GREENFIELD (16 mi away) | 9.6 |
Homes
| Housing units | 21,139 |
| Median year built | 1966 |
| Built before 1980 | 68% |
| Built 2000 or later | 14% |
| Owner-occupied | 79% |
| Median value, owner-occupied | $138,200 |
| Single-family detached | 82% |
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 |
|---|---|---|---|
| Montgomery County, IL | 24 mi | 68% | 88% |
| Greene County, IL | 25 mi | 20% | 51% |
| Jersey County, IL | 27 mi | 22% | 53% |
| Madison County, IL | 30 mi | 33% | 73% |
| Morgan County, IL | 35 mi | 43% | 54% |
| Sangamon County, IL | 37 mi | 58% | 72% |
| Bond County, IL | 37 mi | 47% | 86% |
| Scott County, IL | 39 mi | 27% | 47% |
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