Pacific coast of southwestern Washington in the United States, approximately 20 miles (32 km) long. It drains an area of low hills and a coastal plain into Willapa Bay, a large estuary north of the mouth of the Columbia River.mouthWillapa Bay (Wikipedia)related Mudflats along the Willapa River in Raymondretrieved2023-11-21tagsWillapa RiverRaymond, Washington (Wikipedia)Pacific Ocean (Wikipedia)Washington (state) (Wikipedia)Wikipediawebsitehttps://en.wikipedia.org/wiki/Willapa_River