States / Illinois
Illinois location data
Isopleth answers questions about any coordinate or street address in Illinois with 351 public-data fields from 95 sources: flood and wildfire risk, soils and slope, the power grid, water and roads, climate, and county economics. Each value carries its source, license and vintage. Use it from the REST API or through the MCP server in Claude, ChatGPT, Cursor and other assistants.
Parcel coverage in Illinois
Parcel records: not offered in Illinois. No free statewide parcel layer with clear reuse terms. Every point field on this page still works at any coordinate in Illinois; see parcel coverage for the 35 states plus DC we cover.
Sample values in Illinois
What our API returned at the Census Bureau's interior point of Illinois's 3 largest counties by land area, computed 2026-10-29. One point is not a whole county: values can change within a few hundred meters, so look up your own site. "No data" means the dataset has nothing at that point.
| field | McLean County | LaSalle County | Iroquois County |
|---|---|---|---|
| Hazards | |||
| FEMA flood zone | X | X | X |
| Inside a mapped floodplain | No | No | No |
| Wildfire, annual frequency | 0.000037 events a year | 0.00012 events a year | 0.000025 events a year |
| Tornado, annual frequency | 0.18 events a year | 0.11 events a year | 0.17 events a year |
| Hail, annual frequency | 3.3 events a year | 4.3 events a year | 2.8 events a year |
| On a mapped wetland | No | No | No |
| Nearest mapped wetland | no data | 24 m | 435 m |
| Land | |||
| Elevation | 250 m (820 ft) | 145 m (476 ft) | 197 m (647 ft) |
| Slope | 2.5° | 0.8° | 0.5° |
| Soil drainage | Somewhat poorly drained | Poorly drained | Poorly drained |
| Soil hydrologic group | C/D | C/D | A/D |
| Farmland class | Prime | Prime if conditions met | Prime if conditions met |
| Land use | Agriculture | Forest | Agriculture |
| Crop or cover (CDL) | Soybeans | Herbaceous Wetlands | Corn |
| Dominant crop, 5 years | Soybeans | Corn | Corn |
| Tree canopy | 0% | 52% | 0% |
| On protected land (PAD-US) | No | No | No |
| Surface manager | Private or unknown | Private or unknown | Private or unknown |
| Climate & energy | |||
| Annual precipitation (normal) | 973 mm (38 in) | 934 mm (37 in) | 970 mm (38 in) |
| Days above 32 °C a year | 19 days | 17 days | 19 days |
| Solar resource (GHI) | 4.22 kWh/m²/day | 4.14 kWh/m²/day | 4.17 kWh/m²/day |
| Mean wind speed at 100 m | 7.5 m/s | 6.3 m/s | 7.0 m/s |
| Wind capacity factor | 39% | 34% | 36% |
| Infrastructure | |||
| Nearest transmission line | 1.6 km (1.0 mi) | no data | 791 m |
| Nearest substation (69 kV+) | 4.4 km (2.7 mi) | 3.5 km (2.2 mi) | 8.4 km (5.2 mi) |
| Nearest gas pipeline | 5.9 km (3.7 mi) | 2.9 km (1.8 mi) | 874 m |
| Electric utility | CORN BELT ENERGY CORPORATION | CORN BELT ENERGY CORPORATION | EASTERN ILLINOIS ELEC COOP |
| In a public water service area | No | No | No |
| Depth to water, nearest monitored well | 7.3 m (24 ft) | 12.2 m (40 ft) | 9.4 m (31 ft) |
| Nearest major road | 795 m | 1.1 km (0.7 mi) | 2.4 km (1.5 mi) |
| Community | |||
| Nearest fire station | 5.9 km (3.7 mi) | 1.2 km (0.8 mi) | 9.2 km (5.7 mi) |
| Nearest hospital | 7.5 km (4.6 mi) | 4.7 km (2.9 mi) | 8.8 km (5.5 mi) |
| Nearest school | 4.2 km (2.6 mi) | 2.5 km (1.6 mi) | 2.7 km (1.7 mi) |
| In an Opportunity Zone | No | No | No |
County pages
- McLean County 1,183 sq mi of land
- LaSalle County 1,135 sq mi of land
- Iroquois County 1,117 sq mi of land
Datasets that returned data at these points
| source | fields |
|---|---|
BLM_SMA Bureau of Land Management | surface_management_agency |
EIA_ATLAS U.S. Energy Information Administration | nearest_gas_pipeline_distance_m, nearest_transmission_line_distance_m |
EIA_POWER U.S. Energy Information Administration | electric_utility_service_territory, nearest_substation_distance_m |
EPA_CWS_SERVICE_AREAS U.S. Environmental Protection Agency | within_water_service_area |
FEMA_NFHL Federal Emergency Management Agency | nfhl_flood_zone, within_floodplain_polygon |
FEMA_NRI Federal Emergency Management Agency | hail_annual_frequency, tornado_annual_frequency, wildfire_annual_frequency |
HUD_OPPORTUNITY_ZONES U.S. Department of Housing and Urban Development | in_opportunity_zone |
NOAA_NCEI_NCLIMGRID_DAILY National Oceanic and Atmospheric Administration | days_above_32c_annual_count |
NOAA_NCEI_NORMALS_GRIDDED National Oceanic and Atmospheric Administration | annual_precipitation_normal_mm |
NREL_REV_LANDBASED_WIND_SC_2024 NREL reV supply curves, Open Energy Data Initiative (OEDI) | wind_capacity_factor_pct |
NREL_SOLAR_RESOURCE_V1 NREL Solar Resource Data (NSRDB) | ghi_annual_kwh_m2_day |
NREL_WIND_TOOLKIT NREL WIND Toolkit (Draxl et al., 2015) | mean_wind_speed_100m_ms |
OVERTURE_PLACES © Overture Maps Foundation | nearest_fire_station_distance_m, nearest_hospital_distance_m, nearest_school_distance_m |
OVERTURE_TRANSPORTATION © Overture Maps Foundation, © OpenStreetMap contributors | nearest_major_road_distance_m |
PAD_US USGS Protected Areas Database of the United States (PAD-US) | intersects_protected_area |
USDA_CDL U.S. Department of Agriculture | cdl_class, dominant_crop_5y |
USDA_SSURGO U.S. Department of Agriculture | prime_farmland_classification, soil_drainage_class, soil_hydrologic_group |
USFS_LCMS USDA Forest Service | land_use_class |
USFS_NLCD_TCC USDA Forest Service | tree_canopy_pct |
USFWS_NWI U.S. Fish and Wildlife Service | intersects_wetland, nearest_wetland_distance_m |
USGS_3DEP_COG U.S. Geological Survey | elevation, slope_degrees |
USGS_NWIS_OGC U.S. Geological Survey | nearest_groundwater_well_depth_to_water_m |
These are only the sources behind the fields sampled here. The full list is on Sources & licenses and every field is in the field catalog.
What people use it for in Illinois
- Land buyers: screen a lot for flood zone, wetlands, slope, soils, road and water access before a site visit. Buyers who want it written up can order a $29 report on Check the Land, which is built on Isopleth.
- Solar, wind and data-center siting: distance to transmission and substations, solar and wind resource, protected land.
- Insurance and lending: hazard frequencies and floodplain status for every address in a book.
- Real estate and research: county income, growth and house-price trends next to on-the-ground facts.
See use cases for prompts and the exact fields.
Try it
curl https://api.isopleth.dev/v1/fetch -H "Authorization: Bearer $ISOPLETH_KEY" \
-H "Content-Type: application/json" \
-d '{"lat": 40.494559, "lng": -88.844539, "preset": "site_selection"}'
Or ask your assistant: “Using Isopleth, what are the flood zone, slope and soil drainage at 40.4946, -88.8445?”
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