IDAHO (ante), a mountainous territory of the United States on the Pacific slope of the mountains, embracing many of the sources of the Columbia river; between lat. 42° and 49° n., and Ion. 111° and 117° 10' w.; bounded n. by British Columbia, which it touches only by a narrow strip, w. by Oregon and Washington territory, e. by Montana and Wyoming territories, and s. by Utah and Nevada. The e. line is irregu lar, following most of the way the course of the Rocky and Bitter Root mountains, so that the breadth of the territory, which is in. on the s., is less than 50 im on the north. The length of the territory froth' n. to s. is nearly 500 miles. Its area embraces 86,294 sq.m., or 55,228,160 acres, of which only 16,925,000 acres are suited for agricul ture, and 5,000,000 for grazing; over 14,000,000 acres which are now sterile might be reclaimed by irrigation. The mountain, timber, and mineral lands cover an area of 33,900,000 acres; the lakes 575,000 acres. Its arable portions are chiefly found in the river valleys and around the lakes; and even many of the valleys, notably the ,upper valley of the Salmon river, lie at so great an elevation, and surrounded by such a breadth of lofty snow-capped mountains, that the season between severe ftosts is too short to permit much development of agriculture.
The mountain system of Idaho is peculiar, and its central uplifts are too separate, extensive, and lofty to be ranked as mere spurs of the Rocky mountain chain. The Salmon river range. which occupies the central part of the territory, it portion of which, near the sources of that great river, is known as the Saw-tooth range, is one of the most picturesque and lofty ranges of America. It covers an area as large as the state of New Jersey. The Snake or Shoshone river valley encircles it e., s., and w., and the Sal mon river, w. of Salmon City, on the north. The following large tributaries of the Snake river ail have their sources within a few miles from the junction of lat. with
long. 114° 30', viz.: the Salmon, flowing n.n.w.; the Wood river, flowing s.s.e.; the Little Wood, in the same direction; the Lost river, s.e. ; the e. fork of the Salmon, n.e.; and the sources of the three forks of the Boise river, S.W. It is thus seen that the streams radiate to nearly every point of the compass from this lofty central range, yet all flow into Snake river at last. The government not yet having made a survey of this part of the territory, no map yet published (1880) gives any correct impressions of the sources or directions of the streams which flow from it. The Salmon mountains, like the Alps, are apparently without system or parallelism, and broken into at score of disjointed ranges, through which streams flow in all directions, in tortuous valleys, with intricate exits and entrances. The Wood and Salmon rivers, however, divide these mountain masses into two nearly equal parts by their valleys: Idaho having, as above indicated, it generally n.n.w. direction. The point where the two valleys head is known as the Wood river pass; is nearly 9,000 ft. high, but quite practicable for the construction of either wagon or rail road; while both valleys, to within a few miles of the summit of the pass, are easy planes for roads. These valleys and this pass are therefore the natural passage-way into the heart of Idaho. A road is just completed up the Wind river val ley to within a few miles of the summit of the pass, and will probably be continued over the pass and down the valley of the Salmon to the Yankee fork before this description reaches the eye of the reader. It is at the sources of the streams that flow intothese 11A valleys that extensive discoveries of silver and lead quartz veins, and some gold, have recently been made. The loftier parts of these mountains are generally granite or gneiss, but limestone belts are frequent, especially in the Wind river valley, and out crops of slaty rock are found in many places.