A complete, historic universe of Cook County parcels with attached geographic, governmental, and spatial data.
When working with Parcel Index Numbers (PINs) make sure to zero-pad them to 14 digits. Some datasets may lose leading zeros for PINs when downloaded.
Additional notes:Data is attached via spatial join (st_contains) to each parcel's centroid.
Centroids are based on Cook County parcel shapefiles.
Older properties may be missing coordinates and thus also missing attached spatial data (usually they are missing a parcel boundary in the shapefile).
Newer properties may be missing a mailing or property address, as they need to be assigned one by the postal service.
Attached spatial data does NOT go all the way back to 1999. It is only available for more recent years, primarily those after 2012.
The universe contains data for the current tax year, which may not be complete or final. PINs can still be added and removed to the universe up until the Board of Review closes appeals.
Data will be updated monthly.
Rowcount and characteristics for a given year are final once the Assessor has certified the assessment roll for all townships.
Depending on the time of year, some third-party and internal data will be missing for the most recent year. Assessments mailed this year represent values from last year, so this isn't an issue. By the time the Data Department models values for this year, those data will have populated.
Current property class codes, their levels of assessment, and descriptions can be found on the Assessor's website. Note that class codes details can change across time.
For more information on the sourcing of attached data and the preparation of this dataset, see the Assessor's data architecture repo on GitLab.
Read about the Assessor's 2022 Open Data Refresh.