- Grays Harbor is an estuarine bay located 45 miles (72 km) north of the mouth of the Columbia River, on the southwest Pacific coast of Washington state, in the United States. It is a ria, which formed at the end of the last ice age, when sea levels flooded the Chehalis River. The bay is 17 miles (27 km) long and 12 miles (19 km) wide. The Chehalis River flows into its eastern end, where the city of Aberdeen stands at that river’s mouth, on its north bank, with the somewhat smaller city of Hoquiam immediately to its northwest, along the bayshore. Besides the Chehalis, many lesser rivers and streams flow into Grays Harbor, such as the Hoquiam River and Humptulips River. A pair of low peninsulas separate it from the Pacific Ocean, except for an opening about two miles (3 km) in width. The northern peninsula, which is largely covered by the community of Ocean Shores, ends in Point Brown. Facing that across the bay-mouth is Point Chehalis, at the end of the southern peninsula upon which stands the town of Westport.