The Columbia Plateau is the huge, parched expanse covering Washington, Oregon, and Idaho between the Cascade Range to the west and Idaho's Rockies to the east. To the north the boundary is the Columbia River and the projections of the Columbia Mountains south into the U.S. from Canada, while to the south the border is very indistinct as the Columbia Plateau merges with the Great Basin.
The association between the Pacific Northwest and rain is so strong that few realize that inland from the soaked Cascades the country becomes almost reminiscent of Arizona, with large dry canyons, sagebrush flats, and hot sun. People from Seattle and Portland call the interior the "dry side" and with good reason.
The mountains of the Columbia Plateau are therefore more like those of the Rockies or Great Basin than the Cascades, characterized by sparse forests, generally open terrain, good weather, no glaciers, and long, dusty access roads.
This area is not noted for its mountains, but the Blue and the Wallowa Mountains hold excellent mountain scenery and are among the best-kept secrets in the west.