From its starting point slightly north of Sukakpak Mountain, the river flows generally south or southwest in its upper reaches. The Dalton Highway and the TransAlaska Pipeline run roughly parallel to the river between its source and a point between Twelvemile Mountain, on the river's right, and Cathedral Mountain, on the left, south of Coldfoot. Further south, at Tramway Bar, the river turns generally west to its confluence with the North Fork Koyukuk River.