If you are unfamiliar with Washington's tribes, there are several resources to start with.
Native-Land.ca: This site provides several versions of a map; one shows traditional territory, language family, and/or treaty, depending on the toggles you set. The other, which is new, is a constellation map that focuses on the relationships between tribes. This map is worldwide.
The Tribes of Washington: This site includes information on the 29 federally-recognized tribes who call Washington their home. This resources does not include the six tribes who are not federally recognized, nor tribes whose traditional lands include parts of Washington and Washington, Oregon, or British Columbia.
Nations and Tribes of Washington State: This resource, hosted by the UW American Indian Studies department, lists all of Washington's tribes and links to their homepages. Tribes not federally recognized are designated by an asterisk. This list includes tribes whose lands are partially in other states or British Columbia.
This is Native Land: A permanent exhibit at the Washington State History Museum in Tacoma, This Is Native Land invites visitors to understand Washington State through the lived experiences and voices of its Native people.