Onalaska is a small unincorporated community in Lewis County, Washington, United States. Onalaska is located along Washington State Route 508. Onalaska has a post office with ZIP code 98570. The name for the community comes from the poem, "The Pleasures of Hope" by Scottish poet Thomas Campbell. Onalaska, Washington, Onalaska, Wisconsin, Onalaska, Arkansas and Onalaska, Texas are all historically connected to one another through the lumber industry.