The Parcel 2020 feature contains tax parcel polygons for the 2020 property tax assessment at the County. This feature reflects tax parcel polygons as they existed from 1/1/2020 through 12/31/2020. An ESRI Service is available at: https://hub-cookcountyil.opendata.arcgis.com/datasets/577d80fcbf0441a780ecdfd9e1b6b5c2_0/explore

Parcels with tax assessor data for SSMMA region. See Code Definitions for Cook County parcel classification details.CAVEAT EMPTOR: Cook County data from 2016, Will County data from 2017.We are currently in the process of collecting Cook County data and processing Will County data for 2019.For up-to-date parcel tax records, visit the Cook County GIS Viewer or Will County GIS Viewer, or access the Cook County Tax Assessor's databases [1] [2] or the Will County Tax Assessor's Office.Municipalities in SSMMA's GIS Consortium may contact the GIS staff if more recent data is available to display on municipal viewers.

Private-facing version: https://ssmma-gis.maps.arcgis.com/home/item.html?id=e391d81589c149919cd84a5088d46e80Update log:Jun. 28, 2024 - fixed an issue where taxpayer data showed

The Parcel 2013 feature contains tax parcel polygons for the 2013 property tax assessment at the County. This feature reflects tax parcel polygons as they existed from 1/1/2013 through 12/31/2013. Each parcel is uniquely identified with a Property Index Number (PIN).

The Public Land Survey System (PLSS) is the way land in the United States is subdivided, it forms the foundation of Cook County's cadastral system for identifying and locating land records. Tax parcels are identified using township and section notation, in a modified format. The PLSS serves as a way for users to navigate the parcel geodatabase. This PLSS feature data set is intended to correspond to tax pages on the Cook County Tax Maps. They should not be used for measurement or surveyor purposes. In addition, the parcel attributes PINA (area/township) and PINSA (subarea/section) do not necessarily correspond to the PLSS township and section polygon in which a given parcel resides. The PLSS data is modeled as a single composite network coverage that encompasses townships (area), sections (subarea), quarter sections, and half quarter section. Tax map pages, which typically correspond to half quarter sections (in an east-west split), are modeled as a region subclass in the LANDFABRIC layer. If an indigenous people's reserve was present on the tax map, it was digitized to create subpolygons of the half-quarter section, and those polygons were attributed with the name of the reserve. Within this PLSS data set, a half-quarter section is the smallest polygon unit, except in cases where an Indigenous People's Reserve line is present. The cadastral data for Cook County have previously not been digital nor automated. This project is the initial automation for this information. This database was designed to represent a continuous, non-overlapping spatial database accounting for all land area in Cook County.The PLSS is updated as needed.

The Parcel 2003 feature contains tax parcel polygons for the 2003 property tax assessment at the County. This feature reflects tax parcel polygons as they existed from 1/1/2003 through 12/31/2003. Each parcel is uniquely identified with a Property Index Number (PIN).

The Parcel 2019 feature contains tax parcel polygons for the 2019 property tax assessment at the County. This feature reflects tax parcel polygons as they existed from 1/1/2019 through 12/31/2019. An ESRI Service is available at: https://hub-cookcountyil.opendata.arcgis.com/datasets/3d3375ac11d147308815d5cf4bb43f4e_0

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 monthly. 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. Read about the Assessor's 2025 Open Data Refresh.

The Parcel 2000 feature contains tax parcel polygons for the 2000 property tax assessment at the County. This feature reflects tax parcel polygons as they existed from 1/1/2000 through 12/31/2000. Each parcel is uniquely identified with a Property Index Number (PIN).

Historic land, building, and total assessed values for all Cook County parcels appealed with the Board of Review, from 2010 to present. The Board of Review 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 when the Board of Review closes appeals and certifies the values. • The values in this data are assessed values, NOT market values. Assessed values must be adjusted by their level of assessment (https://prodassets.cookcountyassessor.com/s3fs-public/form_documents/classcode.pdf) to arrive at market value. Note that levels of assessment may have changed throughout the time period covered by this data set. • This data set will be updated when each township is certified. However, note that there may be discrepancies between the Board of Review’s data and the Assessor's site and this data set, as each pull from a slightly different system. • Current property class codes, their levels of assessment, and descriptions can be found on the Assessor's website (https://prodassets.cookcountyassessor.com/s3fs-public/form_documents/classcode.pdf). Note that class codes details can change across time. • The Change Reason and No Change Reason fields are only populated starting with the 2015 year data. All data provided here is prepared for internal purposes by the County of Cook only is provided to the public as a courtesy. While efforts have been made to be as accurate as possible, Cook County provides the data for personal use “as is”. The data is not guaranteed to be accurate, correct, or complete. Information provided should not be used as a substitute for legal, business, tax, or other professional advice. The recipient/viewer should contact appropriate regulating agencies to determine accuracy or suitability of the data for a particular use. This data may not be used in states that do not allow the exclusion or limitation of incidental or consequential damages. Cook County or its staff assume no liability whatsoever for any losses that might occur from the use, misuse, or inability to use its geospatial data, maps or websites. All materials appearing on a map, geospatial data or County web site are transmitted without warranty of any kind and are subject to the terms on this disclaimer.

The feature class LOT contains lot polygons as shown on the tax map.

This is a Cook County Feature class of Unincorporated Zoning District Boundaries (Aggregate). This data is provided by the Cook County Dept. Of Building and Zoning and is maintained by the Cook County Zoning Board of Appeals. Only unincorporated district boundaries are available, please contact specific municipalities for questions regarding incorporated municipal zoning districts.

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 GitHub. Read about the Assessor's 2023 Open Data Refresh.

The Public Land Survey System (PLSS) is the way land in the United States is subdivided, it forms the foundation of Cook County's cadastral system for identifying and locating land records. Tax parcels are identified using township and section notation, in a modified format. The PLSS serves as a way for users to navigate the parcel geodatabase. This PLSS feature data set is intended to correspond to tax pages on the Cook County Tax Maps. They should not be used for measurement or surveyor purposes. In addition, the parcel attributes PINA (area/township) and PINSA (subarea/section) do not necessarily correspond to the PLSS township and section polygon in which a given parcel resides. The PLSS data is modeled as a single composite network coverage that encompasses townships (area), sections (subarea), quarter sections, and half quarter section. Tax map pages, which typically correspond to half quarter sections (in an east-west split), are modeled as a region subclass in the LANDFABRIC layer. If an indigenous people's reserve was present on the tax map, it was digitized to create subpolygons of the half-quarter section, and those polygons were attributed with the name of the reserve. Within this PLSS data set, a half-quarter section is the smallest polygon unit, except in cases where an Indigenous People's Reserve line is present. The cadastral data for Cook County have previously not been digital nor automated. This project is the initial automation for this information. This database was designed to represent a continuous, non-overlapping spatial database accounting for all land area in Cook County.The PLSS is updated as needed.

Park Taxing Districts within Cook County

Hydrographic data was collected for all of Cook County. Significant flowing and standing water features that were visible on the aerial photography were stereocompiled from 1998 aerial photography. The hydrographic midline data set represents, as a single line, the interpreted midline of flowing water features as seen on the aerial photography. The hydrographic midline data layer is used to show the location of the midline of natural drainage features, and is connected to polygonal (standing) hydrographic features such as lakes and ponds. The midline data layer also includes drainage features less than five feet in width, which were not included in the polygon hydrography data set. Midlines were added to water bodies such as double-line rivers to maintain the linear connectivity of the hydrographic network. Where the course of linear features (such as streams and rivers) in the hydrographic midline layer could not be compiled photogrammetrically due to being obscured by other features (such as vegetation or shadows), the obscured line segment was coded as "interpreted". In some cases, a flowing water feature may have run through an underground drain or culvert or its course otherwise obscured from view on the aerial photography. For such cases, in order to maintain linear connectivity of the features, its path was also interpreted and coded as such. Some hydrographic data was provided by the City of Chicago and incorporated into this data layer. These hydrographic data layers are modeled and stored as a network coverage containing polygons and/or lines. This midline data layer was created out of need by Cook County to develop a hydrographic layer in which water features are represented as single lines. The intended primary use of this data layer is for small-scale mapping and networking. The hydrographic midline layer was intersected with the street midline and railroad data layers to create nodes in the coverage model. It was also intersected with the bridge polygon data layer. Where hydrographic midline segments fall within a bridge polygon, they have been given a grade separation code of zero (0) to indicate the water level is technically "at grade". Hydrographic attributes include feature name, tax map name, and type. The primary source of the attribute information was the Cook County Highway Department database. Hydrographic names and alias IDs are linked to lookup tables based on the hydrographic name ID attribute.

Forest Preserve District of Cook County boundaries. To view or use these shapefiles, compression software and special GIS software, such as ESRI ArcGIS, is required.

The feature class Right-of-Way indicates tax exempt rights-of-way digitized from recorded plats.

Fire Protection Taxing Districts in Cook County

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 monthly. 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 2025 Open Data Refresh.