 South Williamsport is located at (41.229179, -77.000464), and is surrounded by the West Branch Susquehanna River to the north (with Williamsport north of the river), Armstrong Township to the east and south, and Duboistown to the west.As the crow flies, Lycoming County is about northwest of Philadelphia and east-northeast of Pittsburgh.According to the United States Census Bureau, the borough has a total area of 2.1 square miles (5.5 km2).1.9 square miles (4.9 km2) of it is land and 0.2 square miles (0.6 km2) of it (11.37%) is water.