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 the current year are only 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 GitHub.

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

For more information on the sourcing of attached data and the preparation of this dataset, see the Assessor's Standard Operating Procedures for Open Data on GitHub.

Commercial valuation data collected and maintained by the Cook County Assessor's Office, from 2021 to present. The office uses this data primarily for valuation and reporting. This dataset consolidates the individual Excel workbooks available on the Assessor's website into a single shared format. Properties are valued using similar valuation methods within each model group, per township, per year (in the year the township is reassessed). This dataset has been cleaned minimally, only enough to fit the source Excel workbooks together - because models are updated for each township in the year it is reassessed, users should expect inconsistencies within columns across time and townships.

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 property-level. Each 14-digit key PIN represents one commercial property. Commercial properties can and often do encompass multiple PINs. Additional notes:

• 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 yearly, once the Assessor has finished mailing first pass values. If users need more up-to-date information they can access it through the Assessor's website.


• The Assessor's Office reassesses roughly one third of the county (a triad) each year. For commercial valuations, this means each year of data only contain the triad that was reassessed that year. Which triads and their constituent townships have been reassessed recently as well the year of their reassessment can be found in the Assessor's assessment calendar.


• One KeyPIN is one Commercial Entity.


• Each KeyPIN (entity) can be comprised of one single PIN (parcel), or multiple PINs as designated in the pins column.


• Additionally, each KeyPIN might have multiple rows if it is associated with different class codes or model groups. This can occur because many of Cook County's parcels have multiple class codes associated with them if they have multiple uses (such as residential and commercial).


• Commercial properties are calculated by first determining a property’s use (office, retail, apartments, industrial, etc.), then the property is grouped with similar or like-kind property types. Next, income generated by the property such as rent or incidental income streams like parking or advertising signage is examined. Next, market-level vacancy based on location and property type is examined. In addition, new construction that has not yet been leased is also considered. Finally, expenses such as property taxes, insurance, repair and maintenance costs, property management fees, and service expenditures for professional services are examined. Once a snapshot of a property’s income statement is captured based on market data, a standard valuation metric called a “capitalization rate” to convert income to value is applied.


• This data was used to produce initial valuations mailed to property owners. It does not incorporate any subsequent changes to a property’s class, characteristics, valuation, or assessed value from appeals.

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

For more information on the sourcing of attached data and the preparation of this dataset, see the As

Situs and mailing addresses of Cook County parcels. Used by the Assessor's office to mail assessment notices.

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:

• Mailing addresses can be out of date or fail to properly reflect deed transfers.


• Newer properties may be missing a mailing or property address, as they need to be assigned one by the postal service.


• This dataset contains data for the current tax year, which may not yet be complete or final. Assessed values for any given year are subject to change until review and certification of values by the Cook County Board of Review, though there are a few rare circumstances where values may change for the current or past years after that.


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


• Data will be updated monthly.

For more information on the sourcing of attached data and the preparation of this dataset, see the Assessor's Standard Operating Procedures for Open Data on GitHub.

This data set contains characteristic data points used by the Cook County Assessor in the 2021 Chicago reassessment to produce initial estimates of the current market value of most Chicago homes (single-family homes, small multi-family homes, and condo units). You can use the "Filter" option to search for a property's PIN or address, and see what data the Assessor’s Office had about a home’s characteristics at the time of modeling*. To learn more about how the 2021 model used this data, read about our public Residential Automated Valuation Model here. Chicago properties not listed here are reassessed using different modeling procedures.

*Important Note: This dataset is, at the time of publication, an early snapshot of data. Data about a home might change later in the assessment process this year as Assessor’s Office staff and analysts review these properties. After this review, updated characteristics and market values are mailed to homeowners. If the data listed on the assessment notice is incorrect, an appeal can be filed to provide the correct characteristics.

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

Metropolitan Water Reclamation Taxing Districts in Cook County

The Parcel 2014 feature contains tax parcel polygons for the 2014 property tax assessment at the County. This feature reflects tax parcel polygons as they existed from 1/1/2014 through 12/31/2014. Each parcel is uniquely identified with a Property Index Number (PIN).

Suburban Cook County Election Precincts maintained by the Cook County Clerk's Election Department. Not included are the City of Chicago Election Precincts which are maintained by the Chicago Board Of Elections. An ArcGIS Service is available at: https://hub-cookcountyil.opendata.arcgis.com/datasets/0e91b48d49744346be343f0cb99d25bd_0/

Voting District Project of the Census Redistricting Data Program commenced in Summer of 2017 to establish the state’s Voting precincts within the bureau’s tiger geography. The initial phase used the Bureau’s GUPS plugin for QGIS to update the districts from the 2010 round, and then a secondary verification phase took place to ensure the updated voting districts were properly enacted into Tiger geographic files. A post census effort took place in December 2021 to cut the number of precincts down countywide to 1430.
Election Data Services conducted Phase 2 of the Census Redistricting Data Program for the State of Illinois, as well as implemented changes made post census in Cook County.

Precincts are updated as needed before every election by the Cook County Clerk's Elections Department.

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