- The Humptulips River is a river in Grays Harbor County, Washington, in the United States. Its main tributaries are the East Fork Humptulips River, about 20 miles (32 km) long (32 km), and West Fork Humptulips River, about 30 miles (48 km) long (48 km). After the forks join, the main river is approximately 20 miles (32 km) long.
