Slope of the Cascade Mountains and the S.
East of the Cascade Mountains the Columbia and Spokane rivers mark the boundary between the Okanogan Highlands to the northward and the Columbia plateau to the southward; The Okanogan Highlands, an outlier of the Rocky Mountains extending westward from the Coeur d'Alene Mountains in Idaho, reach heights of 5000 to 6000 ft.
Both cattle and sheep ranches in the region east of the Cascade Mountains have been considerably encroached upon by the appropriation of lands for agricultural purposes, and the cattle, also, have been forced to the south and east by the grazing of sheep on lands formerly reserved for them; but the numbers of both cattle and sheep on the farms have become much larger.
From the coast to the eastern base of the Cascade Mountains the state is heavily timbered, except in small prairies and clearings in the Willamette and other valleys, and the most important tree is the great Douglas fir, pine or spruce (Pseudotsuga Douglasii), commonly called Oregon pine, which sometimes grows to a height of 300 ft., and which was formerly in great demand for masts and spars of sailing-vessels and for bridge timbers; the Douglas fir grows more commercial timber to the acre than any other American variety, and constitutes about five-sevenths of the total stand of the state.
The Cascade Mountains present a marked example of the effect of relief and aspect on rainfall; they rise across the path of the prevailing westerly winds not far inland from a great ocean; hence they receive an abundant rainfall (80 in.
The Cascade Mountains divide the state topographically into two sharply contrasted parts.
Agriculture and Stock-Raising.--Oregon has some of the most productive agricultural lands in the United States, but they are rather limited in extent, being confined for the most part to the valleys west of the Cascade Mountains and the counties bordering .on the Columbia river east of those mountains.
Of the Cascade Mountains and lying wholly within the state are the John Day river, which rises in the Blue Mountains and enters the Columbia 29 m.
From its mouth are the Cascades, where the river cuts through the lava beds of the Cascade Mountains and makes a descent of about 300 ft.
Slope of the Olympic, Coast range and Cascade Mountains is from 60 to 120 in.