The river rises in Pittsburg, New Hampshire, south of 2,714-foot (827 m) Prospect Mountain, and flows east into Maine. The West Branch of the Little Magalloway joins the Middle Branch 0.7 miles (1.1 km) upstream of the Middle Branch's juncture with the Little Magalloway, itself only 0.3 miles (0.5 km) above that river's end at Aziscohos Lake.