Assessor - 2025 Open Data Refresh

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Description of Open Data available from the Cook County Assessor's Office, with assets newly published in 2025.

Assessor [Archived 05-18-2022] - Residential Assessments

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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.

Assessor [Archived 05-18-2022] - Assessment Appeals by Town and Class - 2010

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Assessment Appeals by Town and Class from Tax Year 2010.

Assessor [Archived 05-11-2022] - Cook County Property Assessments

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Every assessed value in Cook County 2010 to 2020, and appeal indicators. Each PIN has three stages of assessments each year: CCAO Mailed, CCAO Certified, and Board of Review (BOR) Certified final values. This allows comparison in assessments across agencies.

Assessor [Archived 05-11-2022] - Residential Sales Data

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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.

Assessor [Archived 05-11-2022] - First Pass Values

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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

Cook County Clerk - Tax Agency Rates

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Tax Agency rates for Tax Years 2006 through 2013. Data is updated yearly. For more information on Tax agencies visit the Cook County Clerk's website at: http://www.cookcountyclerk.com/tsd/Pages/default.aspx

Cook County Clerk - Taxing Agencies with Tax Rates - 2010

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This dataset is now depricated in favor of: https://datacatalog.cookcountyil.gov/Property-Taxation/Cook-County-Clerk-Tax-Agency-Rates/9sgn-ibhu. Cook county taxing agencies and their final 2010 tax rates.

How To Use Open Data

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Overview of Cook County's Open Data site, including what users need an account to access and links out to detailed guides

Other Open Data Resources

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Overview of state and municipality open data resources, separate from Cook County