County GIS · State lines · October 20, 2026
Illinois–Wisconsin Border Counties and Their Parcel Maps
All 12 counties on the Illinois–Wisconsin line, with seats, 2023 populations and a link to each official parcel map, plus what changes at the state line.
Looking for the counties on the Illinois–Wisconsin border and their parcel maps? According to the Census Bureau's county adjacency file, 6 Illinois counties touch 6 Wisconsin counties along the line. Each one keeps its own property records and its own parcel viewer, so land near the line often means checking two counties in two states.
A farm, hunting tract or lake lot can sit in one state while the road, the neighbors or the rest of the property are in the other. This page lists every county that touches the line on either side, with links to each official parcel map.
Illinois–Wisconsin border at a glance
- Counties on the line: 12 (6 in Illinois, 6 in Wisconsin)
- With a verified public parcel viewer in our directory: 12 of 12
- Residents, 2023 estimates: about 1,420,545 on the Illinois side and 542,893 on the Wisconsin side
- Most populous on each side: Lake County, IL (708,760) and Kenosha County, WI (167,488)
- Largest by land area: McHenry County, IL (603 sq mi) and Grant County, WI (1,147 sq mi)
Illinois counties on the line
| County | Seat | Land (sq mi) | 2023 pop. | Parcel viewer |
|---|---|---|---|---|
| Boone County | Belvidere | 281 | 53,202 | ArcGIS Map Viewer |
| Jo Daviess County | Galena | 601 | 21,756 | county web map |
| Lake County | Waukegan | 444 | 708,760 | county web map |
| McHenry County | Woodstock | 603 | 312,800 | county web map |
| Stephenson County | Freeport | 564 | 43,105 | county web map |
| Winnebago County | Rockford | 513 | 280,922 | county web map |
Wisconsin counties on the line
| County | Seat | Land (sq mi) | 2023 pop. | Parcel viewer |
|---|---|---|---|---|
| Grant County | Lancaster | 1,147 | 51,409 | ArcGIS |
| Green County | Monroe | 584 | 36,951 | ArcGIS Experience Builder |
| Kenosha County | Kenosha | 272 | 167,488 | county web map |
| Lafayette County | Darlington | 634 | 16,945 | ArcGIS Instant Apps |
| Rock County | Janesville | 718 | 164,278 | ArcGIS Instant Apps |
| Walworth County | Elkhorn | 555 | 105,822 | county web map |
Which counties face each other
The Census adjacency file pairs counties that share a boundary. Use it to find the county across the line from the one you know:
- Boone County, IL borders Rock County, WI, Walworth County, WI
- Jo Daviess County, IL borders Grant County, WI, Lafayette County, WI
- Lake County, IL borders Kenosha County, WI
- McHenry County, IL borders Kenosha County, WI, Walworth County, WI
- Stephenson County, IL borders Green County, WI, Lafayette County, WI
- Winnebago County, IL borders Green County, WI, Rock County, WI
What changes when you cross the line
- Different viewers. On the Illinois side the official maps run on: county web map (5); ArcGIS Map Viewer (1). On the Wisconsin side: county web map (2); ArcGIS Instant Apps (2); ArcGIS (1); ArcGIS Experience Builder (1). Search boxes, parcel ID formats and the details shown in pop-ups will differ.
- Different records offices. Deeds, plats and tax bills are kept by the county where the parcel sits.
- Different rules. Zoning, septic permits and property tax are set locally and by each state, so check with the county on the side where you plan to build or buy.
Researching a tract that crosses the line
- Find the parcel in both counties' viewers. Each side will show only its own piece, with its own parcel number.
- Pull the recorded deed from each county's register or recorder, since each county records only the land inside its own boundary.
- Expect two tax bills, one from each county, and check each state's rules for homestead or farm exemptions.
- For a sale, a fence or a building permit, hire a licensed surveyor familiar with the line; tax-map lines are drawings, not surveys.
A quick way to check which side a spot is on
Tap the spot on the Platbookmapper Land Map. Its land report names the county and links straight to that county's parcel viewer, plus FEMA flood, USGS elevation, USDA soil and wetland results.
Related guides
More: Illinois counties · Wisconsin counties
Sources
- U.S. Census Bureau county adjacency file, used for which counties share the line.
- U.S. Census Bureau Gazetteer files, 2020 county land area.
- U.S. Census Bureau, Population Estimates Program, county totals, Vintage 2023 (July 1, 2023 estimates)
- Platbookmapper county GIS directory (live data file behind our county pages, pulled October 20, 2026) for each county's official parcel viewer.
- County seats: Wikidata (county seat property), cross-checked against Census place names.