THE ROCKY MOUNTAINS, giving to that term the wide extension which is generally applied to it in the United States, occupy a con siderable area in Montana, Idaho, Wyoming, Colorado, and New Mexico. Between the various ranges of which they are composed, lie many intermontane valleys and parks that have been covered over by material brought down from the surrounding uplands. In many of these the land is suitable for pastoral purposes, and with the aid of irrigation sufficient fodder can be grown to serve for winter food. A small quantity of cereals (less than 1 per cent. of the United States crop) and a considerable quantity of beet for sugar, are also grown on the irrigated lands, which are gradually being extended. The tendency is therefore towards a somewhat larger and more settled population than there has been in the past.
The mineral wealth is varied and extensive. Coalfields are found at intervals in a belt of country stretching along the eastern base of the Rocky mountains, and in another, but more restricted, belt along the western base, while in the intervening park regions there are numerous isolated basins. The coal, which ranges in character from lignite to anthracite, is worked chiefly in Colorado and Wyoming, but also in Montana and New Mexico. The product which exceeds 20,000,000 tons, is largely used by the railways, and in the mining and smelting industries.
Gold to the annual value of about £6,000,000 is obtained from this region, Colorado (with two-thirds of that amount), Utah, and Montana being the chief producing states. In Colorado, the famous Cripple Creek district in the western foot-hills of Pike's Peak, a region of great volcanic activity in Tertiary times, produces one-half of the output of the state. On the western slopes of the Wahsatch Mountains in Utah and in Montana, gold is also found, frequently associated with silver, copper, and lead. Nearly two thirds of the silver produced in the United States comes from the Rocky Mountain region. In Colorado the most important district is that round Leadville in the Mosquito Range, at the headwaters of the Arkansas River ; in Utah silver occurs in copper and lead ores in the Wahsatch Mountains in the vicinity of Great Salt and Utah lakes ; in the north of Idaho it is chiefly associated with lead, and in Montana with copper. Copper is worked chiefly in Montana and Utah. The former supplies about one-fourth of the United States' output of that mineral, the district around Butte producing practically the whole of that amount. The mining district of Utah yields the greater part of the remainder of the Rocky Mountain output. Forty per cent. of the lead mined in the United States is obtained in the north of Idaho and in Utah.