The Cispus River is about 54 miles (87 km) long and flows into the Cowlitz River at Lake Scanewa in the Cascade Mountains of Washington. Its tributaries drain most of south-central and southeastern Lewis County, extreme northeast Skamania County, and some of western Yakima County.Its main stem begins in Lewis County in a high, glacial valley to the north of Snowgrass Flats in the Goat Rocks Wilderness, located on the Gifford Pinchot National Forest.