County GIS · State lines · October 19, 2026
Maryland–Pennsylvania Border Counties and Their Parcel Maps
All 17 counties on the Maryland–Pennsylvania line, with seats, populations and each official parcel map, plus what changes at the line.
Looking for the counties on the Maryland–Pennsylvania border and their parcel maps? According to the Census Bureau's county adjacency file, 8 Maryland counties touch 9 Pennsylvania 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.
Maryland–Pennsylvania border at a glance
- Counties on the line: 17 (8 in Maryland, 9 in Pennsylvania)
- With a verified public parcel viewer in our directory: 17 of 17
- Residents, 2023 estimates: about 1,936,558 on the Maryland side and 2,095,545 on the Pennsylvania side
- Most populous on each side: Baltimore County, MD (844,703) and Lancaster County, PA (558,589)
- Largest by land area: Frederick County, MD (661 sq mi) and Somerset County, PA (1,075 sq mi)
Maryland counties on the line
| County | Seat | Land (sq mi) | 2023 pop. | Parcel viewer |
|---|---|---|---|---|
| Allegany County | Cumberland | 422 | 67,273 | Maryland FINDER Online (MD Dept. of Planning) |
| Baltimore County | Towson | 598 | 844,703 | county web map |
| Carroll County | Westminster | 448 | 176,639 | Maryland FINDER Online (MD Dept. of Planning) |
| Cecil County | Elkton | 346 | 105,672 | Maryland FINDER Online (MD Dept. of Planning) |
| Frederick County | Frederick | 661 | 293,391 | Maryland FINDER Online (MD Dept. of Planning) |
| Garrett County | Oakland | 649 | 28,423 | Maryland FINDER Online (MD Dept. of Planning) |
| Harford County | Bel Air | 437 | 264,644 | Maryland FINDER Online (MD Dept. of Planning) |
| Washington County | Hagerstown | 458 | 155,813 | Maryland FINDER Online (MD Dept. of Planning) |
Pennsylvania counties on the line
| County | Seat | Land (sq mi) | 2023 pop. | Parcel viewer |
|---|---|---|---|---|
| Adams County | Gettysburg | 519 | 106,748 | PASDA Pennsylvania Tax Parcels viewer |
| Bedford County | Bedford | 1,012 | 47,350 | ArcGIS Web AppBuilder |
| Chester County | West Chester | 751 | 549,784 | county web map |
| Fayette County | Uniontown | 791 | 123,915 | county web map |
| Franklin County | Chambersburg | 772 | 157,854 | PASDA Pennsylvania Tax Parcels viewer |
| Fulton County | McConnellsburg | 438 | 14,468 | ArcGIS Web AppBuilder |
| Lancaster County | Lancaster | 944 | 558,589 | ArcGIS Web AppBuilder |
| Somerset County | Somerset | 1,075 | 72,197 | ArcGIS Web AppBuilder |
| York County | York | 904 | 464,640 | ArcGIS Experience Builder |
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:
- Allegany County, MD borders Bedford County, PA, Fulton County, PA, Somerset County, PA
- Baltimore County, MD borders York County, PA
- Carroll County, MD borders Adams County, PA, York County, PA
- Cecil County, MD borders Chester County, PA, Lancaster County, PA
- Frederick County, MD borders Adams County, PA, Franklin County, PA
- Garrett County, MD borders Fayette County, PA, Somerset County, PA
- Harford County, MD borders Lancaster County, PA, York County, PA
- Washington County, MD borders Franklin County, PA, Fulton County, PA
What changes when you cross the line
- Different viewers. On the Maryland side the official maps run on: Maryland FINDER Online (MD Dept. of Planning) (7); county web map (1). On the Pennsylvania side: ArcGIS Web AppBuilder (4); PASDA Pennsylvania Tax Parcels viewer (2); county web map (2); 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
- Maryland county GIS websites by viewer
- Maryland plat maps
- Pennsylvania county GIS websites by viewer
- Pennsylvania plat maps
More: Maryland counties · Pennsylvania 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 19, 2026) for each county's official parcel viewer.
- County seats: Wikidata (county seat property), cross-checked against Census place names.