The Umpqua River (UHMP-kwah) on the Pacific coast of Oregon in the United States is approximately 111 miles (179 km) long. One of the principal rivers of the Oregon coast, it drains an expansive network of valleys in the mountains west of the Cascade Range and south of the Willamette Valley, from which it is separated by the Calapooya Mountains. The "Hundred Valleys of the Umpqua" form the timber-producing heart of southern Oregon centered on Roseburg. The river flows entirely within Douglas County, which encompasses most of the watershed of the river from the Cascades to the coast.