County GIS · State lines · October 20, 2026
Montana–Wyoming Border Counties: Parcel Maps on Both Sides
All 12 counties on the Montana–Wyoming 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 Montana–Wyoming border and their parcel maps? According to the Census Bureau's county adjacency file, 6 Montana counties touch 6 Wyoming 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.
Montana–Wyoming border at a glance
- Counties on the line: 12 (6 in Montana, 6 in Wyoming)
- With a verified public parcel viewer in our directory: 12 of 12
- Residents, 2023 estimates: about 171,643 on the Montana side and 153,594 on the Wyoming side
- Most populous on each side: Gallatin County, MT (126,409) and Campbell County, WY (47,498)
- Largest by land area: Big Horn County, MT (4,998 sq mi) and Park County, WY (6,939 sq mi)
Montana counties on the line
| County | Seat | Land (sq mi) | 2023 pop. | Parcel viewer |
|---|---|---|---|---|
| Big Horn County | Hardin | 4,998 | 12,751 | Montana Cadastral (Montana State Library) |
| Carbon County | Red Lodge | 2,048 | 11,419 | Montana Cadastral (Montana State Library) |
| Carter County | Ekalaka | 3,340 | 1,418 | Montana Cadastral (Montana State Library) |
| Gallatin County | Bozeman | 2,605 | 126,409 | ArcGIS Experience Builder |
| Park County | Livingston | 2,802 | 17,903 | ArcGIS Experience Builder |
| Powder River County | Broadus | 3,298 | 1,743 | Montana Cadastral (Montana State Library) |
Wyoming counties on the line
| County | Seat | Land (sq mi) | 2023 pop. | Parcel viewer |
|---|---|---|---|---|
| Big Horn County | Basin | 3,137 | 12,018 | TerraGIS |
| Campbell County | Gillette | 4,802 | 47,498 | Beacon (Schneider Geospatial) |
| Crook County | Sundance | 2,854 | 7,592 | ArcGIS Experience Builder |
| Park County | Cody | 6,939 | 30,735 | TerraGIS |
| Sheridan County | Sheridan | 2,523 | 32,519 | TerraGIS |
| Teton County | Jackson | 3,997 | 23,232 | TerraGIS |
Which counties face each other
Here is who borders whom across the line, based on the Census Bureau adjacency file:
- Big Horn County, MT borders Big Horn County, WY, Sheridan County, WY
- Carbon County, MT borders Big Horn County, WY, Park County, WY
- Carter County, MT borders Crook County, WY
- Gallatin County, MT borders Park County, WY, Teton County, WY
- Park County, MT borders Park County, WY
- Powder River County, MT borders Campbell County, WY, Crook County, WY, Sheridan County, WY
What changes when you cross the line
- Different viewers. On the Montana side the official maps run on: Montana Cadastral (Montana State Library) (4); ArcGIS Experience Builder (2). On the Wyoming side: TerraGIS (4); Beacon (Schneider Geospatial) (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
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: Montana counties · Wyoming 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.