The Big Fork River watershed covers 1,326,947 acres. The river flows north 165 miles from Dora Lake (45 miles northeast of Bemidji in north-central Itasca County) to the Rainy River, which forms the Minnesota/Canadian border. This confluence is 16 miles west-southwest of International Falls. Nearly 60% of the watershed is land owned or managed by the state.
Development pressure is moderate in most areas, with occasional farms being parceled out for development, recreation, or country homes.