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.

2021 assessor neighborhoods used by the Cook County Assessor's Office for valuation and reporting.

Neighborhood polygons used by the Cook County Assessor's Office for valuation and reporting. These neighborhoods are specific to the Assessor. They are intended to represent homogenous housing submarkets, NOT Chicago community areas or municipalities.

These neighborhoods were reconstructed from individual parcels using spatial buffering and simplification. The full transformation script can be found on the Assessor's GitLab.

Residential condominium unit characteristics collected and maintained by the Assessor's office for all of Cook County, from 1999 to present. The office uses this data primarily for valuation, assessments, and reporting.

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 unit-level. Each 14-digit PIN represents one condominium unit. The first 10 digits of each PIN are the condominium building. Additional notes:

• The Assessor's Office has historically not tracked any internal, unit-level characteristics for condominiums, including square footage, number of bedrooms, etc. In 2021, the office began to manually compile unit-level data from a variety of sources. The ultimate intention is to gather basic data on all condominium units in the county.


• As such, unit square footage, building total square footage, and unit number of bedrooms are only available on a per-triad basis after 2021. Future data updates will add these features for other areas.


• Condominiums are assessed based on their percentage of ownership. See the link below for more information on how this process works. The percentage of ownership for all units in a building should sum to 1. However, this may not always be the case in this data, since it does not include commercial units.


• Condominium parcels can also be parking areas, storage units, or common areas. Identifying these units can be challenging, and they are not valued using mass appraisal. The Assessor's Office has an ongoing effort to clean up and identify these unit records.


• 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.


• Data will be updated bi-weekly.


• 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.


• Rowcount and characteristics for a given year are final once the Assessor has certified the assessment roll for all townships.

For more information on how this data is used to estimate condominium unit values, see the Assessor's condominium modeling code on GitLab.

Township codes can be found in the legend of this map.