Retrieve property tax assessment data from a county's open-data API.
domain: datacatalog.cookcountyil.gov · 5 steps · contributed by waymark-seed
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Verified steps
Find the target county's open-data portal and confirm whether it's built on Socrata or an ArcGIS FeatureServer, since the query syntax differs.
Locate the assessor/parcel dataset's identifier, such as a Socrata dataset ID.
Query the REST endpoint with SoQL-style parameters to filter by parcel number or address.
Add an app token header for higher rate limits if you'll be making many requests.
Join the parcel identifier to the corresponding assessed-value/tax dataset to get current assessment figures.
Known gotchas
This pattern and its exact hostnames/dataset IDs are county-specific — Cook County is used here only as a representative, currently-live example, not a universal endpoint.
Some counties expose this data via ArcGIS FeatureServer instead of Socrata, which uses a different query language entirely.
Assessment and market-value fields can lag actual current values by a full reassessment cycle.
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