The Map Unit draws the official tax maps for Cook County. This includes using the legal description of the properties throughout the county to establish the Property Index Number (PIN) for each parcel for taxation purposes.
The Map Unit maintains records of taxing district boundaries to provide the basis for property tax calculations done for tax extensions, as well as the voting district boundaries used by the Clerk for election purposes.
The county tax maps, once commonly referred to as the "Sidwell Maps," are updated each year, reflecting the divisions, subdivisions and consolidations of property processed annually by the Cook County Assessor's office. The maps show the boundaries of each parcel and identify the unit numbers within each condominium development in conformity with the condominium declaration recorded with the county.
Know your PIN
To make any inquiries about your property taxes, it is important to know your property index number. The PIN is a 14-digit code that is unique for each property.
Click Here to learn how to use your PIN.
Maps forms online
Other services provided by the Maps Unit
- Affixes tax certifications to plats of subdivision or dedication.
These required certifications must be affixed to plats prior to being recorded to attest that there are no tax delinquencies on the parcel(s) affected. The fee is $10 per plat.
- Reviews proposed plats affecting land in unincorporated Cook County.
Plats for unincorporated land require approval by the Cook County Board of Commissioners, with prior review by the Map Unit's manager, who serves as plat officer for the Board.
- Provides digitized version of tax maps for purchase.
Pursuant to Cook County ordinance, the Clerk's office is now able to provide digitized versions of the official county tax map for sale to interested parties for a base fee of $30,000. Developed as part of a larger county-wide Geographic Information System (GIS),the maps are copyrighted and are subject to restrictions on transfers to third-parties, though transfer can be authorized by license and payment of a royalty fee. Please contact the Clerk's Map Department at 312/603-5640 for further information.
Need more help?
Go to the Tax Glossary or Frequently Asked Questions.