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.


• Due to decrepencies between the systems used by the Assessor and Clerk's offices, tax_district_code is not currently up-to-date in this table.

For more information on the sourcing of attached data and the preparation of this dataset, see the Assessor's data architecture repo on GitLab.

Historic land, building, and total assessed values for all Cook County parcels, from 1999 to present. The Assessor's Office uses these values for reporting, evaluating assessment performance over time, and research.

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.

This data is parcel-level. Each row contains the assessed values for a single PIN for a single year. Important notes:

• Assessed values are available in three stages: 1) mailed, these are the initial values estimated by the Assessor's Office and mailed to taxpayers. 2) certified, these are values after the Assessor's Office closes appeals. 3) Board of Review certified, these are values after the Board of Review closes appeals.


• The values in this data are assessed values, NOT market values. Assessed values must be adjusted by their level of assessment to arrive at market value. Note that levels of assessment have changed throughout the time period covered by this data set.


• This data set will be updated roughly contemporaneously (monthly) with the Assessor's website as values are mailed and certified. However, note that there may be small discrepancies between the Assessor's site and this data set, as each pulls from a slightly different system. If you find a discrepancy, please email the Data Department using the contact link below.


• This data set contains data for the current tax year, which may not be complete or final. PINs can still be added and removed to the universe and values can change up until the Board of Review closes appeals.


• Rowcount and characteristics for a given year are final once the Assessor has certified the assessment roll for all townships. Values should be considered final once the Board of Review closes its appeals, though there are a few rare circumstances where values may change for the current or past years after that.


• 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.

Read about the Assessor's 2022 Open Data Refresh.

The Parcel 2015 feature contains tax parcel polygons for the 2015 property tax assessment at the County. This feature reflects tax parcel polygons as they existed from 1/1/2015 through 12/31/2015. Each parcel is uniquely identified with a Property Index Number (PIN).

The bid tabulations provided herein are preliminary and are for informational purposes only. The purpose of providing this preliminary information is to improve process transparency. The information contained in the preliminary bid tabulations is subject to change pending math review, analysis of all bids, and review of documentation provided.
Bids: All bids estimated at $25,000 or more are publicly opened and read at the time, date, and place specified in the bid document.
RFP/RFQ/RFI: Responses to RFP/RFQ/RFI are not publicly opened. Names of respondents will be made available based on the names identified on the sealed package and is, therefore, subject to change.

For bid tabulations before June 2016 see https://datacatalog.cookcountyil.gov/d/pn38-yupm

The update script for this dataset is currently broken. Please see the Cook County Clerk SEI Search for recent filings. For extended information about Statements of Economic Interests in Cook County IL, visit the Cook County Clerk's SEI search: http://ethics.cookcountyclerk.com/PublicSearch/

As of February 14, 2020 this dataset will be considered archived information and will no longer be updated.

First-pass property values as assessed by the Cook County Assessor in their Computer Assisted Mass Appraisal system used to assess residential properties. This dataset contains first pass values for 2019 and corresponds with residential PINs in the Cook County Assessor's Assessment Data. These are NOT final assessed values. For Disclaimers, see dataset narrative at https://datacatalog.cookcountyil.gov/stories/s/p2kt-hk36

The Commission investigates, mediates and, if warranted, adjudicates violations of the Cook County Human Rights Ordinance. If you believe that you have been the victim of unlawful discrimination in the protected areas of employment, housing, public accommodations, credit or access to County programs, services or contracts, contact the Cook County Commission on Human Rights for an intake interview. https://www.cookcountyil.gov/service/complaint-filing-and-investigation