East Washington is a rectangular plateau, set in a frame of mountains, and drained by the Columbia River and its tributaries. The Cascade Range being the west side of the frame, the north side is formed by irregular spurs which run out at right angles from the Cascade Mountains along the Canada border, and connect with the Cabinet Mountains. The east side of the frame is in Idaho, and consists chiefly of the Coeur d'Alene Mountains. On the south lie the Blue Mountains, which are partly in Washington Territory, but chiefly in Oregon. The mountains on the north have a few peaks 5,000 to 9,000 feet high, and many of the dividing ridges are high, steep and rugged. Much of the region is described, however, as high plateau country, dotted over with small, conical mountains. It abounds in streams of water, generally small. A strip of arable land runs on the east side of the Columbia River from the mouth of the Spokane River to the mouth of the Colville River and the valleys of Colville and the Little Spokane River are highly spoken of as agricultural regions. The elevation of these river valleys is from 1,200 to 1,600 feet above tide-water. [Sidenote: Coeur d'Alene Mountains.] Passing to the east side, we find the plateau country at its north corner extending to the Idaho line where the foot-hills of the Rocky Mountains begin, and soon rise into the Coeur d'Alene Mountains, which--being the local name for part of the Bitter Root Range--is a part of the western branch of the Rocky Mountains. The Coeur d'Alene River and Lake belong to the Columbia River basin, and are so naturally connected in mining and trading interests with Washington Territory, that in another connection I shall have much to say of the Coeur d'Alene country, as also of the Colville country, and other parts of the mountain rim. South of the Coeur d'Alene Lake the plateau country extends far into Idaho, and gives to that State its best farming lands. The Blue Mountains which mark the southern limit of the plateau in Washington Territory do not extend more than half-way across the plain, leaving a long projection of the plateau to extend southward into Oregon. [Sidenote: The Great Plateau.] [Sidenote: Coulées.]