Pennsylvania Borders: States, Map & Complete Guide

New York and Pennsylvania share a border along Pennsylvania's northern edge. The boundary runs roughly east-west from Lake Erie to New Jersey, with portions following rivers and surveyed lines.

The Pennsylvania-New York border extends for about 300 miles from Lake Erie in the west to the Delaware River in the east. The border follows a combination of the 42nd parallel and natural features. Pennsylvania counties along this border include Erie, Crawford, Warren, McKean, Potter, Tioga, Bradford, Susquehanna, Wayne, and Pike. The border region includes portions of the Allegheny Mountains and the northern tier of Pennsylvania.

New Jersey and Pennsylvania are separated entirely by the Delaware River along Pennsylvania's eastern edge. This river creates one of the most important boundaries in the northeastern United States.

The Pennsylvania-New Jersey border follows the Delaware River for about 130 miles from New York in the north to Delaware in the south. The entire border is a water boundary with the river flowing through scenic valleys and gaps in the mountains. Pennsylvania counties along this border include Pike, Monroe, Northampton, Bucks, and Philadelphia. The Delaware Water Gap is a famous natural feature along this border. Philadelphia sits directly on this river boundary.

Delaware borders Pennsylvania in a small area in Pennsylvania's southeastern corner. This is Pennsylvania's shortest state border, forming part of a unique circular boundary.

The Pennsylvania-Delaware border runs for about 23 miles. The northern portion of this border follows a unique 12-mile circular arc centered on the courthouse in New Castle, Delaware—the only circular state boundary in the United States. Pennsylvania counties along this border are Chester and Delaware. The small tri-state area where Pennsylvania, Delaware, and Maryland meet sits at the southern end of this border.

Maryland forms Pennsylvania's southern border along the famous Mason-Dixon Line. This historic boundary has enormous cultural and historical significance in American history.

The Pennsylvania-Maryland border runs for about 230 miles from Delaware in the east to West Virginia in the west. The Mason-Dixon Line was surveyed between 1763 and 1767 by Charles Mason and Jeremiah Dixon to settle a boundary dispute. The line later became the symbolic division between free and slave states before the Civil War. Pennsylvania counties along this border include York, Adams, Franklin, Fulton, Bedford, and Somerset. The border follows a carefully surveyed latitude line.

West Virginia borders Pennsylvania in the southwestern region. Rivers and the Mason-Dixon Line extension form portions of this boundary.

The Pennsylvania-West Virginia border extends for about 160 miles. The border includes portions of the Mason-Dixon Line and river boundaries. The Ohio River forms part of the border in the northwest. Pennsylvania counties along this border include Greene, Washington, and Fayette. Pittsburgh sits near this border region. The border area includes parts of the Appalachian Plateau.

Ohio borders Pennsylvania on the western side. The boundary combines a straight north-south meridian line with river sections:.

The Pennsylvania-Ohio border runs for about 90 miles from Lake Erie in the north to West Virginia in the south. The border primarily follows a meridian line surveyed in the early 1800s, with the Ohio River forming a small section in the southwest. Pennsylvania counties along this border include Erie, Crawford, Mercer, Lawrence, and Beaver. Youngstown, Ohio and Pittsburgh, Pennsylvania are major cities near this border.

Lake Erie forms Pennsylvania's northwestern boundary from Ohio in the west to New York in the east. Pennsylvania's narrow Lake Erie coastline is the state's only Great Lakes access.

Pennsylvania's Lake Erie shoreline stretches about 51 miles—the shortest of any Great Lakes state. Only Erie County in Pennsylvania touches Lake Erie. The city of Erie, Pennsylvania's fourth-largest city, sits on this shore and serves as the state's only port on the Great Lakes. Presque Isle State Park extends into Lake Erie, creating a natural harbor. Despite its short coastline, Pennsylvania's Lake Erie access has been vital for commerce and industry.