The Grundy County tax map is available free online through the county’s GIS Property Viewer at maps.grundyco.org, where you can search any parcel by address or parcel number and see its boundaries against aerial imagery.1Grundy County. Geographic Information Systems (GIS) For assessment values, tax amounts, and sale history tied to that same parcel, the county runs a separate Property Tax Inquiry tool through DevNet.2DevnetWedge. Grundy County Property Tax Inquiry Paper copies and corrections go through the Supervisor of Assessments at the courthouse in Morris.
Search a Parcel Online
Start with the Property Viewer when you want to see the land itself. Click a parcel on the map or type in an address, and the viewer returns the parcel outline, its index number, and its position relative to neighboring lots. You can pan across townships and zoom in to the lot-line level. The GIS gallery also publishes standalone maps for flood hazard areas, county roads, and school, fire, and legislative districts.
Switch to the DevNet Property Tax Inquiry when you need numbers rather than geography. It searches by parcel number, owner name, street address, sale price range, or sale date range, with advanced filters for tax codes, tax districts, townships, and legal descriptions.2DevnetWedge. Grundy County Property Tax Inquiry There is a dedicated search for mobile home numbers, and the system links to a portal for paying taxes online.
A rule of thumb: use the viewer to answer “where is it,” and use DevNet to answer “what does it owe.”
Reading a Parcel on the Map
Each parcel carries a unique index number, also called a Parcel Identification Number or PIN. That number is the thread connecting the physical land to every tax bill, deed record, and assessment card on file. Under the Illinois Property Tax Code, the numbering system describes property by township, section, block, and parcel or lot, and may cross-reference a street address when one exists.3Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 200/9-45 – Property Index Numbering In counties with fewer than three million residents, including Grundy, the county board directs either the chief county assessment officer or the recorder to assign them.
The map itself shows boundary lines between adjoining parcels, lot dimensions where land has been formally subdivided, and the general layout of road and utility right-of-way corridors. Subdivided residential lots tend to be drawn with precise linear measurements. Larger agricultural tracts are identified mainly by legal description.
The PIN stays with the parcel regardless of ownership. Buy a property and the same number follows you. A new number is assigned only when a parcel is subdivided, merged, or otherwise legally reconfigured, which is what makes the system reliable for tracking tax obligations across decades of ownership changes.
Getting a Paper Copy
If you need a printed tax map sheet for a real estate closing, a permit application, or a boundary dispute, the Supervisor of Assessments office handles those requests. The office is in the Grundy County Courthouse at 111 E. Washington Street in Morris, and is open Monday through Friday from 8:00 a.m. to 4:30 p.m.4Grundy County. Supervisor of Assessments You can reach staff by phone at (815) 941-3269 or by email at Assessments@grundycountyil.gov.
Have the parcel number or subdivision name ready so staff can pull the correct sheet quickly. Fees vary by size and format of the print, and by whether you need an official certification. Call ahead to confirm current pricing and whether the office can produce the format you need on the spot or needs processing time.
Fixing an Error on the Map
Tax maps are only as good as the records behind them. If a parcel boundary, acreage figure, or lot dimension on the map does not match your deed or a licensed survey, the error can carry through to your assessed value and your tax bill. The first step is to contact the Supervisor of Assessments office with documentation showing the discrepancy. A recorded survey or plat from a licensed surveyor carries the most weight, because it provides an independent measurement of the land.
If the error has already affected your assessment, the Board of Review can issue a certificate of error to correct the record.5Grundy County. Grundy County Board of Review A certificate of error is a different track than a regular assessment appeal. It fixes an objective mistake, such as wrong square footage or a parcel recorded in the wrong township, rather than a disagreement over market value. Ask the office which process fits your situation, because the filing requirements and timelines differ.
Appealing an Assessment Tied to the Map
If a map error has inflated your valuation, or you otherwise believe your property is overassessed, file a written complaint with the Grundy County Board of Review. The Board hears complaints that property is incorrectly assessed, equalizes assessments between property classes, and issues certificates of error when mistakes are found.5Grundy County. Grundy County Board of Review
The deadline is 30 calendar days after the publication of the assessment list.6Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 200/16-55 – Assessment Complaints For the 2025 tax year, assessment notices were mailed on October 29, 2025, with a December 1, 2025, filing deadline.5Grundy County. Grundy County Board of Review Watch for the published dates each year, because missing the window means waiting until the next assessment cycle.
Your complaint must be in writing, identify the specific property, and be filed in duplicate. If you are arguing that the map reflects incorrect acreage or lot dimensions, bring a recent survey, your deed, or any plat that shows the correct measurements. The Board cannot raise your assessment without first giving you notice and an opportunity to respond.6Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 200/16-55 – Assessment Complaints If the Board’s decision does not resolve the issue, Illinois has a Property Tax Appeal Board that provides a second level of review.