The Willapa or Willoopah, also known as Kwalhioqua, were a Northern Athapaskan-speaking people in southwestern Washington, United States. Their territory was the valley of the Willapa River and the prairie between the headwaters of the Chehalis and Cowlitz Rivers.
Together with the Clatskanie (Tlatskanai) in the upper Nehalem River Valley and along the headwaters of the Klaskanine and Clatskanie River in northwestern Oregon they spoke dialects of the now extinct Kwalhioqua-Clatskanie (Kwalhioqua–Tlatskanai) language, the Willapa dialect was the most divergent. The Kwalhioqua lived north of the lower Columbia River, the Clatskanie (Tlatskanai) to the south, separated by the territory of the Lower Chinook-speaking Shoalwater Bay Chinook (or Willapa Chinook) or Clatsop and the Kathlamet (Cathlamet), which spoke an other Chinookan variant. The Kwalhioqua-Clatskanie people were dispersed among Coast Salish peoples in the 19th century and their language was extinct before the 1930s.” Victor Golla, Atlas of the World’s Languages 2007 pg. 17
The Willapa or Kwalhioqua had two subdivisions or subgroups:
the Suwal on headwaters of the Chehalis River – called by the Lower Cowlitz and Upper Chehalis Ohwilaph.
the Wela’pakote’li or Willapa on Willapa River – called by the Lower Cowlitz and Upper Chehalis Swilaumsh.