County GIS · State lines · October 20, 2026
Illinois–Iowa Border Counties: Parcel Maps on Both Sides
All 15 counties on the Illinois–Iowa 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–Iowa border and their parcel maps? According to the Census Bureau's county adjacency file, 7 Illinois counties touch 8 Iowa 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–Iowa border at a glance
- Counties on the line: 15 (7 in Illinois, 8 in Iowa)
- With a verified public parcel viewer in our directory: 15 of 15
- Residents, 2023 estimates: about 271,777 on the Illinois side and 462,206 on the Iowa side
- Most populous on each side: Rock Island County, IL (141,236) and Scott County, IA (174,270)
- Largest by land area: Hancock County, IL (794 sq mi) and Clinton County, IA (695 sq mi)
Illinois counties on the line
| County | Seat | Land (sq mi) | 2023 pop. | Parcel viewer |
|---|---|---|---|---|
| Carroll County | Mount Carroll | 445 | 15,526 | county web map |
| Hancock County | Carthage | 794 | 17,186 | ArcGIS Experience Builder |
| Henderson County | Oquawka | 379 | 6,088 | county web map |
| Jo Daviess County | Galena | 601 | 21,756 | county web map |
| Mercer County | Aledo | 561 | 15,487 | myGISonline |
| Rock Island County | Rock Island | 427 | 141,236 | ArcGIS Map Viewer |
| Whiteside County | Morrison | 684 | 54,498 | ArcGIS Experience Builder |
Iowa counties on the line
| County | Seat | Land (sq mi) | 2023 pop. | Parcel viewer |
|---|---|---|---|---|
| Clinton County | Clinton | 695 | 46,158 | Beacon (Schneider Geospatial) |
| Des Moines County | Burlington | 416 | 38,253 | county web map |
| Dubuque County | Dubuque | 608 | 98,887 | Beacon (Schneider Geospatial) |
| Jackson County | Maquoketa | 636 | 19,342 | Beacon (Schneider Geospatial) |
| Lee County | Fort Madison, Keokuk | 518 | 32,565 | Beacon (Schneider Geospatial) |
| Louisa County | Wapello | 402 | 10,513 | Beacon (Schneider Geospatial) |
| Muscatine County | Muscatine | 437 | 42,218 | Beacon (Schneider Geospatial) |
| Scott County | Davenport | 458 | 174,270 | Beacon (Schneider Geospatial) |
Which counties face each other
Here is who borders whom across the line, based on the Census Bureau adjacency file:
- Carroll County, IL borders Clinton County, IA, Jackson County, IA
- Hancock County, IL borders Lee County, IA
- Henderson County, IL borders Des Moines County, IA, Lee County, IA
- Jo Daviess County, IL borders Dubuque County, IA, Jackson County, IA
- Mercer County, IL borders Des Moines County, IA, Louisa County, IA
- Rock Island County, IL borders Clinton County, IA, Louisa County, IA, Muscatine County, IA, Scott County, IA
- Whiteside County, IL borders Clinton County, IA
What changes when you cross the line
- Different viewers. On the Illinois side the official maps run on: county web map (3); ArcGIS Experience Builder (2); myGISonline (1); ArcGIS Map Viewer (1). On the Iowa side: Beacon (Schneider Geospatial) (7); county web map (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
Open the Platbookmapper Land Map, search the nearest county, and tap the spot. The land report shows which county it falls in, along with flood zone, elevation, soil and wetlands, and links to that county's parcel map.
Related guides
More: Illinois counties · Iowa 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.