Mountain Top Mountain Top, once named Penobscot, PA, is located at 41°8′7″N 75°54′16″W / 41.13528°N 75.90444°W (41.1353022, -75.9044749) in the shadow of Mount Penobscot (or Penobscot Knob). According to the United States Census Bureau, the CDP has a total area of 15.1 square miles (39.0 km2), all of it land.

Mountain Top is located in the saddle pass atop the drainage divide between the Susquehanna River basin (to the north and west) and the Lehigh River basin (to the east and south), so sits astride an important land communications corridor bridging the two watersheds below. It is just 8 miles northwest of White Haven, at the head end of the Lehigh River, and in the heights above Hazleton, only 10 miles south of Wilkes-Barre on Pennsylvania Route 309. Consequently, even though regional railroads are much diminished in scope and influence, Mountain Top yard, once used as a marshaling yard at the top of the Ashley Planes funicular (cable driven) railway, is still an important regional element of the transportation infrastructure connecting Allentown and Philadelphia with points north and west via trackage to several yards in New York State.

Mountain Top is elevated at 1,558 feet above sea level.