It rises in the high Cascades north of Fish Mountain, formed by the confluence of two short forks in eastern Douglas County approximately northwest of Crater Lake. It flows generally southwest through a remote canyon in the Umpqua National Forest to Tiller, then west past Milo and Days Creek. It emerges into the South Umpqua Valley at Canyonville, passing under Interstate 5 and flowing north along the highway past Tri-City, Myrtle Creek, and Roseburg. It joins the North Umpqua from the south to form the Umpqua approximately northwest of Roseburg.