The Lewis River is a tributary of the Columbia River, about 95 miles (153 km) long, in southwestern Washington in the United States. It drains part of the Cascade Range north of the Columbia River. The drainage basin of the Lewis River covers about 1,046 square miles (2,709 km2). The river's mean annual discharge is about 6,125 cubic feet per second (173.4 m3/s). Unlike nearby Lewis County and Fort Lewis the Lewis River was not named for Meriwether Lewis, but rather for A. Lee Lewis, an early settler who homesteaded near the mouth of the river.