The North River begins on South Branch Mountain in Hardy County and flows northeast for 47 miles before joining the Cacapon River at the Forks of Cacapon. It is the Cacapon's largest tributary.

The river flows through forested hills and wide farmland valleys. The area was settled early through land grants issued by Lord Fairfax. Historically, the Great Wagon Road used to cross the river here, on its way west from Virginia. Settlers used the river's resources for industries like tanneries (using tree bark to process hides) and lime kilns (using local limestone for building and farming). The river also powered the gristmills that helped give the town of North River Mills its name.