Not very far. They border each other.
About 150 road miles.
It is 158.90 miles according to MapQuest.
Chester, Pennsylvania is 54.1 miles from Aberdeen, Maryland in a motor vehicle.
The widest point of Maryland occurs at its northern border with Pennsylvania. The measured width there is about 250 miles.
The states surrounding West Virginia are Kentucky, Virginia, Maryland, Pennsylvania, and Ohio. From Charleston it's 133 miles to Ohio, 176 miles to Kentucky, 234 miles to Virginia, 287 miles to Pennsylvania, and 281 miles to Maryland.
The driving distance from Ambler, Pennsylvania to Lexington Park, Maryland is 195 miles.
The air distance from Silver Spring, Maryland, to Lebanon, Pennsylvania, is 99 miles. That equals 159 kilometers or 86 nautical miles.
It is 105.71 miles according to MapQuest.
Delaware, Maryland, and Pennsylvania
The distance from Philadelphia, Pennsylvania to Annapolis, Maryland is about 90 miles (144 km).
197 miles / 316 km
It is 247.81 miles according to MapQuest.