Kwalhioqua-Clatskanie was an Athabascan language once spoken by
the Willapa, Suwal, and Clatskanie tribes of Oregon and Washington state. These tribes were decimated by smallpox in the early 1800's,
and the survivors merged into neighboring tribes. Though there are still Clatskanie and Kwahlioqua descendents among other Indian tribes
of northwest Oregon, they have not survived as distinct nations, and the language has not been spoken since the 1930's.
Only a few remnants of it remain, and they can be hard to find. If you're looking for information on Kwalhioqua-Clatskanie,
your only reliable source is likely to be Alexander Anderson's vocabularies from the 1850's, usually filed under "Klatskanai" or "Tah-cully."
Try a university library.