Pennsylvania sits in the Mid-Atlantic, a keystone linking Northeast, Midwest, and South. Its borders are a mix of colonial charters, river lines, and lake frontage.
| State | Border Type | Key Feature |
|---|---|---|
| New York | North | 42nd parallel (mostly), Lake Erie corner |
| New Jersey | East | Delaware River (entire length) |
| Delaware | Southeast | Delaware River & Bay; famous “Twelve-Mile Circle” arc |
| Maryland | South | Mason-Dixon Line (surveyed 1763–67) |
| West Virginia | Southwest | Mountain ridges, split from VA in 1863 |
| Ohio | West | Ohio River (PA owns to low-water mark on OH side) |
| Water Body | Role |
|---|---|
| Delaware River | Forms entire PA–NJ border; tidal to Trenton |
| Delaware Bay | PA’s tiny SE corner touches it (via river mouth) |
| Atlantic Ocean | No direct coastline — but tidal Delaware R. connects |
| Lake Erie | 51 mi shoreline (Erie County) — PA’s only Great Lake |
| Ohio River | Forms PA–WV & PA–OH borders; major barge corridor |
| Susquehanna River | Bisects state; largest river on East Coast draining to Atlantic |
PA’s southern border (Mason-Dixon) was the first scientifically surveyed intercolonial boundary — and became the cultural North/South divide.