Willapa Bay, one of the largest and most healthy estuaries in the continental United States, is situated in southwestern Washington State, fifteen miles north of the mouth of the Columbia River. This shallow bay off the mighty Pacific Ocean is thirty miles long and five miles wide at it's widest.

Willapa Bay is sheltered from the open Pacific by the Long Beach peninsula and its waters are fed by the Nasalle, Willapa, and North Fall Rivers. Rainfall in this area is over 90 inches per year, which percolates and filters through the heavily forested Douglas-fir, western hemlock, western red cedar and Sitka spruce of the coastal temperate rainforest. This lowland coastal forest is extremely productive, making it particularly rich in both habitat and biological diversity.

Including the Bay, the Willapa watershed covers 680,000 acres and is a major wildlife resource. Its wetlands provide critical habitat for over seventy species of migratory birds and the waters here are one of the five largest oyster-producing areas in the world. The waters and tidelands are also home to other shellfish species, such as crabs and clams, as well as Chum, Coho and Chinook salmon.

Significant parts of the watershed have been set aside in the Willapa National Wildlife Refuge. The reserve was established in 1937 to protect parts of the Long Beach Peninsula from being dredged, filled or polluted. The refuge encompasses 11,200 acres of marshland, upland forests, pastures and tidal estuary. The refuge's tidal flats contain one quarter of the productive shellfish waters of the western United Sates. Oysters and other shellfish species are cultivated on over 10,000 acres of privately owned or leased tidelands.