IDAHO (Indian, 'Mountain Gem'), one of the Northwestern States of the United States. Its extreme length from north to south along western border is 485 miles. The width vanes from 50 miles in the northern part where it borders on the Dominion of Canada to about 300 miles in the south. The total area is approximately 84,000 square miles of which about 534 is water surface. The capital is Boise.
Topography.— Idaho is widely diversified topographically, having many hills and moun tains, interspersed with fertile valleys, rugged canyons, mountain gorges, wide upland mead ows and wooded parks, broad plateaus, rolling prairies, sage brush plains, great rivers with cascades and cataracts, beautiful lakes with jetting bays, studded with great pines and Douglas fir. The Cabinet, Cceur d'Alene and Bitter Root mountains, principal spurs of the great Rockies, form the eastern boundary separating Idaho and Montana. From these mountain chains spurs are sent out west and southwest through nearly every part of the State to the great plains of the Snake River Basin which extends in crescent shape across the southern part from east to west and forms nearly half the west central boundary separat ing Idaho from the States of Oregon and Wash ington. The Boise, Payette, Salmon and Clear water rivers, all affluents of the Snake, drain the central part of the State. The Spokane, Pend d'Oreille and Kootenai rivers make out let for the waters of the beautiful lakes of Cceur d'Alene, Pend d'Oreille, Kaniksu and Spirit Lake, all in the extreme northern part. A small portion of the southeastern part is drained through the Bear River into Salt Lake. This river also forms an outlet for Bear Lake, a beautiful body of water about half of which lies in the extreme southeastern part and ex tends into Utah.
Climate.— Idaho extends through seven de grees of latitude. Its altitude ranges from about 700 feet to more than 12,000 feet. Its northern end lies within the path of the rain areas which pass eastward from the north Pacific Ocean while the southern portion lies well out of that path. As a result of these
complex factors the climate is so diverse as to render description difficult and accurate graphic representation impracticable. The lower Snake, Salmon and Clearwater River valleys have a very pleasant and equable climate. The higher valleys have most agreeable summers with long winters and heavy snowfall. The tem perature of Idaho is varied, ranging from 108 degrees above in summer to 45 degrees below zero in winter. The mean temperature is 56 degrees. The normal annual precipitation is about 17 inches, ranging from 37 inches in Shoshone County in the northern part of the State, to six inches in the southern section.
The rock from which the soil of central and southern Idaho was derived is known as the Columbia River lava, or basalt. There were successive flows of this lava, as is demonstrated by intervening sedimentary de posits. Above the lava the soil is fine and of a dark color, while the subsoil, of equally fine texture, is always of dark yellow or brownish color without pebbles or sand grains. The soils on the older lavas are usually light colored and contain sand and fragments of rocks and minerals. In the region of the great inter mountain plateau along the course of the Snake River the soils consist of the fine, silty foams, formed through the weathering of the rolling basaltic country at higher levels, or they con sist of ash-like and silty loams of ancient lake beds within which volcanic ash was deposited to great depths. Wherever water is available for the irrigation of these lands they have proven wonderfully fertile for the production of gen eral and special crops. On the basaltic uplands heavy yields of grain and vegetables are ob tained without irrigation. The soil of the northern part of the State is sandy and of a clayey loam less fertile yet it produces good crops without irrigation.