Located in the double ranched of the Olympic and Cascade Mountains, the Columbia Basin is the warmest and driest region of the state. Originally carved by glaciers and slowly eroded over time by the Columbia River, the basin was further sculpted about 12,000 years ago by a series of violent flows known as the Spokane Floods. The floods left behind strange basaltic rock formations known as the Channeled Scablands. The basin is characterized by native shrub-steppe vegetation and thousands of acres of ponds and marshes created by irrigation water from the Columbia Basin Project. Southwest Washington includes the vast wheatfields of the Palouse Hills and the rugged Blue Mountains which straddle the border between Washington and Oregon.

Wildlife of this region include the golden eagle, prairie falcon, and other species commonly found in high shrub-steppe deserts of the West. The Columbia Basin is also a magnet for thousands of ducks, geese, and migratory wading birds that nest and winter in this vast system of ponds and marshes. The Blue Mountains harbor a variety of wildlife species found in dry mountain areas, including mule deer, bighorn sheep and Rocky Mountain elk.