You will have to go through all of these and read which are native. Unfortunately a lot of species here have been introduced at some time in the past, like the eastern gray squirrels.
http://www.washington.edu/burkemuseum/collections/mammalogy/mamwash/mamwash.html
the most dry land region is columbia plateau
I believe it is the Columbia Plateau.
The population of the Columbia Plateau region in the United States is approximately 1.6 million people. This region covers parts of Washington, Oregon, and Idaho and includes cities such as Spokane, Kennewick, and Yakima.
The major features of the Columbia Plateau in Washington include extensive basalt plateaus, canyons carved by the Columbia River, and the unique basalt columns at places like the Palouse Falls. The region also features fertile agricultural lands, such as the Palouse region, known for its wheat production.
The Columbia Plateau is a geographic region in Washington and Oregon characterized by a high, flat plateau that was formed by ancient volcanic activity. It is known for its fertile soils, which support agriculture and wine production. The area is also home to the Columbia River, which has played a significant role in shaping the landscape and providing water for irrigation.
Washington has 5 mainland regions. Coastal Region, Puget Sound Lowlands, Cascade Mountains, Okanogan Highlands, Columbia Plateau.
Columbia is located on the Piedmont Plateau.
The rockymountains region, Columbia plateau region and the basin and range region.
The largest geographic area in eastern Washington is the Columbia Plateau, which covers much of the region and extends into Idaho and Oregon. The plateau is characterized by rolling hills, basalt cliffs, and fertile farmland, making it an important agricultural region in the state.
The rockymountains region, Columbia plateau region and the basin and range region.
1. The Olympic Peninsula Region 2. The Yakima River Drainage Region 3. The Puget Sound Basin Region has Seattle 4. The Columbia River Basin. 5. Willapa Hills Region 6. The Cascade Mountain Region 7. Okanogan Highlands 8. the Blue Mountain Region has
The Indians of the Southwest lived in an arid region, while the Columbia Plateau region received abundant rainfall.