Query Illinois water wells via the ISGS ILWATER ArcGIS MapServer
domain: maps.isgs.illinois.edu · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Query Illinois water/related wells with GET https://maps.isgs.illinois.edu/arcgis/rest/services/ILWATER/Water_and_Related_Wells/MapServer/2/query?where=<predicate>&outFields=*&f=json - layer 2 is "Water and Related Wells" (layers 0/1 are label layers, layer 3 is core samples).
Supported query output formats are JSON, geoJSON, and PBF - pass f=geojson if you want GeoJSON directly instead of Esri JSON.
Respect the service's maxRecordCount of 2000 records per request; use resultOffset/resultRecordCount to page through the roughly 390,000 total records.
Check the /legend and /layers child resources to confirm current field names before writing a query, since ISGS periodically updates the schema.
For bulk/custom statewide extracts beyond what live queries handle well, ISGS also offers a paid data-package service (per-well-header fee, delivered by email/FTP) referenced on the ISGS geological records page.
Known gotchas
The layer mixes water wells, engineering borings, and outcrops together - filter on a well-type/category field if you only want water wells, not all record types.
Spatial reference is EPSG:4269 (NAD83), not the more common EPSG:4326 - reproject if combining with WGS84 data.
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