Public ArcGIS MapServer endpoint for Cook County parcel data. URL, supported fields, and a working sample query, copy it, or open it directly in the UrbanKit parcel lookup tool.
Beyond the parcel record, Cook County has a free Chicago property report: code violations and building permits for an address, read straight from the city's open data.
Free Chicago property report: code violations + building permits →https://gis12.cookcountyil.gov/traditional/rest/services/CookViewer3Parcels/MapServer/0PIN1010-digit Property Index NumberPIN14_dash14-digit PIN (XX-XX-XXX-XXX-XXXX)street_addressStreet Addresscurl -s 'https://gis12.cookcountyil.gov/traditional/rest/services/CookViewer3Parcels/MapServer/0/query?where=PIN14_dash%3D%2717-09-128-001-0000%27&outFields=PIN10,PIN14_dash,street_address&returnGeometry=false&f=json'
https://gis12.cookcountyil.gov/traditional/rest/services/CookViewer3Parcels/MapServer/0/query?where=PIN14_dash='17-09-128-001-0000'&outFields=PIN10,PIN14_dash,street_address&returnGeometry=false&f=jsonOpen this URL in a browser tab to see the raw ArcGIS JSON response.
| Field name | Label | Searchable |
|---|---|---|
| PIN10 | 10-digit Property Index Number | YES |
| PIN14_dash | 14-digit PIN (XX-XX-XXX-XXX-XXXX) | YES |
| street_address | Street Address | YES |
Cook County uses the 14-digit PIN format (XX-XX-XXX-XXX-XXXX), exposed as PIN14_dash on this layer. The legacy cookVwHosted/Cook_County_Parcels/FeatureServer was retired in 2026; the active replacement is CookViewer3Parcels/MapServer/0 (1.86M+ parcels). Public fields are geometry, PIN10, PIN14_dash, and street_address only. Owner name is NOT on this layer. For ownership lookups, use the Cook County Property Tax Portal at cookcountypropertyinfo.com, keyed by PIN. Cook County reassesses on a triennial cycle divided into three geographic triads: the City of Chicago triad, the north suburban triad, and the south/west suburban triad. Each triad goes through a full reassessment every three years on a rotating schedule (north triad reassessed 2025, south/west triad 2026). The county has 5.2M+ residents and 1.86M taxable parcels, the largest county in Illinois by both metrics. The Assessor's office is the valuation authority; the Treasurer's office (cookcountytreasurer.com) handles tax payment records.
Cook County GIS Department, https://www.cookcountyil.gov/agency/geographic-information-systems-gis
Cook County's Parcels layer exposes parcel identifiers (10-digit Property Index Number, 14-digit PIN (XX-XX-XXX-XXX-XXXX)) and address fields (Street Address). Use it for address-to-PIN lookups and identifier queries. All 3 listed fields accept queries. Served as an ArcGIS MapServer layer, which supports query operations but not write operations; last verified 2026-05-15.
/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.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 Cook County actually publishes, not what you might expect from a national standard (there isn't one).
For background, see What is an APN?
gis12.cookcountyil.gov serves Cook County, Illinois parcels over public ArcGIS REST, but, like most county servers, it may not send the CORS headers a browser needs for a cross-origin fetch. If a direct browser call fails, the layer still works from curl, Postman, or a server-side script; the UrbanKit parcel lookup tool proxies the request, so a search that succeeds there confirms the layer is genuinely public.
We last verified Cook County's MapServer layer on 2026-05-15. County GIS teams move services without notice, so if you hit a fresh 404, tell us and we'll re-check. Atlas entries are re-verified on a rolling basis.
Cook County's layer is hosted by the county on gis12.cookcountyil.gov. Public ArcGIS endpoints rarely rate-limit individual reads, but gis12.cookcountyil.gov can throttle heavy automated traffic at the host level. Page through results with resultOffset / resultRecordCount and request only the fields you need. There's no API key and no charge from the county.