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ATLAS · COUNTY·IL·FIPS 17111

McHenry County, IL
parcel REST API.

McHenry County parcel REST endpoint not yet listed.

No public REST endpoint listed yet

McHenry County does not have a verified public ArcGIS REST parcel endpoint in our directory. Many counties run their parcel layers on the assessor's portal or behind a viewer-only interface. If you know the URL, send it in.

How to find an ArcGIS parcel layer URL →

— Notes

McHenry County's ArcGIS server at mchenrycountygis.org/arcgis/rest/services/parcels/MapServer previously exposed a public parcel layer with ParcelNumber, Owner, SiteAddressStreet, and SiteAddressCity fields — Google's index still shows cached query URLs returning those fields. As of 2026-05-11 all direct REST requests to that server return HTTP 403 Forbidden, including the service descriptor. This appears to be a recent firewall change. The county's open-data Hub (data-mchenrycountygis.opendata.arcgis.com) references GeoServices links but the backing server is now restricted. Recommend contacting gis@mchenrycountyil.gov or rechecking the endpoint in 30–60 days.

— Source

McHenry County GIS — https://data-mchenrycountygis.opendata.arcgis.com/

How to use this REST endpoint

Two paths from URL to result

Open in Parcel Lookup — click the button on the endpoint card. The lookup tool loads the layer, auto-detects fields, and gives you a search box. No code, no API keys, just a browser.
Query directly — append /query?where=…&outFields=*&f=jsonto the URL. The sample query above is a working example you can paste into a browser tab to see the raw JSON response.

Why field names vary by county

Counties publish parcel data through their own ArcGIS Server installations, each with its own schema. One county uses APN, another uses PIN, a third uses PARCEL_ID. Some expose owner names; others keep them on a separate assessor's portal. The searchable fields list above reflects what this county actually publishes — not what you might expect from a national standard (there isn't one).

For background, see What is an APN?

What to do with the results

Generate a public-notice mailing list — pipe the parcel layer URL into Radius Notice to buffer around an address and select neighboring owners.
Print Avery 5160 labels — export the result CSV and drop it into CSV → Labels.
Pull individual parcel records — use Parcel Lookup directly to grab zoning, assessed value, and ownership for one property at a time.

Quick FAQs

This URL gives me a CORS error in my own app — what now?

Many county servers allow public reads but block browser cross-origin requests. The UrbanKit parcel lookup tool fetches directly from your browser; if it works there, the layer is technically public. For your own integration, you may need a same-origin proxy or server-side fetch.

The endpoint loaded last week and now returns 404. Did the URL change?

Possibly — counties move services without warning. We re-verify entries weekly and flag stale ones. If you're seeing a fresh 404, please let us know and we'll update the listing.

Are these endpoints free to query at scale?

Most are. Public ArcGIS layers don't typically rate-limit individual reads, but heavy programmatic use can trigger throttling at the host level. Be respectful — query what you need.

View all FAQs →

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McHenry County, ILparcel REST API.