| MASONDIXONLINE | The boundary line between Maryland and Pennsylvania, USA (5-5,4) |
| DIOMEDEISLANDS | Two small land masses in the Bering Strait, separated by the boundary line between the US and Russia (7,7) |
| MASON | Charles, surveyor, with Jeremiah Dixon, of the boundary between Maryland and Pennsylvania (5) |
| DIXON | Jeremiah ___, English surveyor best known for his work with Charles Mason on resolving a boundary dispute between Maryland and Pennsylvania (5) |
| POTOMAC | River that forms part of the borders between Washington, DC and Virginia and between Maryland and Virginia |
| MARGIN | The boundary line or the area immediately inside the boundary. |
| AVES | Maryland and Pennsylvania, in D.C. |
| DREDGE | Unearth the doctor from the boundary line (6) |
| CIRCUMFERENCE | It goes all the way round the boundary line (13) |
| OUTOFBOUNDS | Over the boundary line in Aussie Rules (3,2,6) |
| THREEMILE | And 21 Location of a nuclear generating station on the Susquehanna River in Pennsylvania, US, noted for a partial meltdown in 1979 (5,4,6) |
| CHESAPEAKEBAY | Bordered by Maryland and Virginia, the largest inlet of the Atlantic coast of the US (10,3) |
| CHESAPEAKE | And 12 Inlet of the Atlantic in Maryland and Virginia, US (10,3) |
| KNIFEEDGE | Precarious (but sharply defined) boundary line! (5-4) |
| ISLAND | Location of a nuclear generating station on the Susquehanna River in Pennsylvania, US, noted for a partial meltdown in 1979 (5,4,6) |
| PHILADELPHIA | City in Pennsylvania, US, that saw the signing of the Declaration of Independence in 1776 (12) |
| SCRANTON | Major city in Pennsylvania, US, on the Lackawanna River (8) |
| BAY | Inlet of the Atlantic in Maryland and Virginia, US (10.3) |
| CHICKEN | Meat used in the dishes Maryland and Marengo (7) |
| LIMIT | Boundary line (5) |
