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GIS/Mapping Division  

Understanding Tax Assessment Parcel Maps

Tax Assessment Parcel Maps are required to support the county’s tax assessment function. The property tax system operates on a tax assessment year basis, so these maps are published annually, to correspond to that cycle. The maps include all changes resulting from legal records submitted to the Recorder of Deeds up to December 31st of the preceding year, as well as any court orders, municipal annexations and other transactions which impact the maps. The legend on each map page states the last tax assessment year in which that page changed. It is possible that a given page might not have any changes for a period of years, whereas others may be updated every year based on the legal documents filed with the county.

Tax Assessment Parcel Maps are a visual inventory of real property for assessment purposes. The maps are based on information contained in recorded legal documents. The maps themselves are not intended to, and do not, determine actual property ownership boundaries on the ground. A professional land surveyor registered to practice in the State of Illinois is needed to determine the actual location of property boundaries on the ground. In compiling these maps county staff must reconcile sometimes conflicting information in surveys, plats of subdivision and other legal documents going back to the early 19th century. The accuracy of this information can vary significantly. The final map represents the best judgment of our staff based on the accumulation of evidence in cases where information is incomplete, unclear metes and bounds or conflicting surveys. A Property Index Number is assigned to each tax assessment parcel. This is a unique number which does not change as long as that parcel is not subdivided, consolidated or grouped with other adjacent parcels under the same ownership for tax billing purposes. The county maintains a PIN history which extends back to the inception of the PIN numbering system in the early 1970’s.

The ten digit PIN is structured as follows:




1 - 2

Survey Township 01 – 17

3 - 4

Section Number 01 – 36


Quarter Section 1 – 4

5 - 7

Block Number

8 - 10

Parcel Number


Example: PIN 0817304014 can be interpreted as follows: Township 08, Section 17, Block 304, Parcel 014. Note that the first digit of block, “3” in this example, signifies that the parcel lies in quarter section 3. The quarter sections are labeled from 1 through 4, representing the northwest, northeast, southwest and southeast quarter sections, respectively.

The three digit parcel number appears on the map within each parcel’s boundaries.

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Phone 847.377.2373
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GIS and Mapping Division
18 N County St 6th Floor
Waukegan, IL 60085
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