Single and multi-family (less than 7 units) property 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 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. 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. This data is improvement-level - 'improvements' are individual buildings on a parcel. Each row in a given year corresponds to a building e.g. two rows for the same parcel in one year means a parcel has more than one building. Data will be updated bi-weekly. Rowcount and characteristics for the current year are only 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. NOTE: The Assessor's Office has recently changed the way Home Improvement Exemptions (HIEs) are tracked in its data. HIEs "freeze" a property's characteristics for a period of time with the intention of encouraging owners to improve their property without fear of assessment increases. Historically, the updated, "improved" characteristics were saved in a separate file. However, in more recent years, the improved characteristics are saved in the main characteristics file. As such, the records in this data set from before 2021 do NOT include HIE characteristic updates, while those after and including 2021 DO include those updates. For more information on HIEs, see the Assessor's Data Department wiki. For more information on how this data is used to estimate property values, see the Assessor's residential 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. Read about the Assessor's 2023 Open Data Refresh.

Assessment dataset used by the Cook County Assessor in their Computer Assisted Mass Appraisal (CAMA) system used to assess residential properties in Northern Triennial Townships. This dataset contains property information for every residential PIN in the northern triennial townships where class is within a specified list of classes. For disclaimers, see dataset narrative at https://datacatalog.cookcountyil.gov/stories/s/p2kt-hk36

Cook County 10-digit parcels with attached distances to various spatial features. When working with 10-digit Parcel Index Numbers (PINs) make sure to zero-pad them to 10 digits. Some datasets may lose leading zeros for PINs when downloaded. 10-digit PINs do not identify individual condominium units. Additional notes:,

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.

This data contains every residential Property Index Number (PIN) and corresponding Assessed Values from significant stages in the assessment process. This data was replaced with the more comprehensive Cook County Assessor's Fair Cash Values.

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:,

This is the data set of residential sales used by the Cook County Assessor in their Computer Assisted Mass Appraisal system used to assess residential property values. This data set contains property information for every arm's-length residential sale in Cook County where class is within a specified list of classes. For disclaimers, see data set narrative at https://datacatalog.cookcountyil.gov/stories/s/p2kt-hk36 This data set was replaced by the more comprehensive data set Cook County Assessor's Sales.

Historical permit data submitted by municipalities to the Cook County Assessor's Office. 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:,

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:,