Missouri system from the Columbia River system, these two receiving the drainage of the State. The Missouri River springs from three main headstreams in the extreme southwestern portion and in Yellowstone Park. It flows first northward along the eastern base of the mountains, then eastward through the great plains to the eastern boundary, just beyond which it receives its first large tributary, the Yellowstone, which drains the southeastern quarter of the State. The Clark Fork of the Columbia River, with its two main branches, the Missoula and the Flathead, drains the great western basin, the latter branch flowing through Flathead Lake, the only lake of considerable size in the State. Both the Missouri and the Yellowstone are navigable for small boats more than 300 miles from the boundary, and the Clark Fork is also navigable for some distance into Montana. The railroads, however, have supplanted the rivers as means of communication.
Climate. The climate is in general very dry, healthful, and exhilarating. There is a great annual range of temperature, in general from 30° and 40° below zero to over 100° above. At some stations the temperature has been more than 60° below zero, while the same locality may have an annual range of over 150°. The average mean temperature for the State is 70° for the warmest and 11° for the coldest month. The extreme cold of winter is often tempered by the warm and dry chinooks (q.v.), which blow in a northeasterly direction from the mountain ranges and absorb a large amount of moisture from the snow they melt. Blizzards occur only in the eastern plains, and tornadoes are unknown. The rainfall is generally insufficient to support agriculture without irrigation, amounting to only about 12 inches per annum.
Soil and Vegetation. The principal valleys are characterized by fine level meadows with a rich loamy soil, and are occupied by extensive cattle ranges. The eastern plains are almost treeless prairies, the river courses alone being fringed with willow, cottonwood, and similar trees. There are extensive forests of conifers in the mountain region of the western half of the State, amounting in 1900 to about 42,000 square miles, or 29 per cent. of the State's area. A considerable portion of this, however, has been burned over. The National Government has reserved forest areas within the State amounting to 7875 square miles. The product in 1900 was valued at $2,949,992. Yellow pine, red fir, and tamarack are the principal varieties.
For Fauna, see paragraphs under Rocky Mountains and United States.
Geology and Minerals. The eastern and western halves of the State differ widely in their geological structure. The eastern plains consist mainly of undisturbed strata of Cretaceous and Tertiary rocks, the latter forming the extreme eastern portion. Narrow belts of Jurassic and Carboniferous rocks skirt the Cretaceous formations on the west along the base of the mountains. The mountainous half has a complex structure, with much folding and faulting. In the south the Archæan granite cores and outpourings of Tertiary lava predominate on the surface, while north of the Missouri the main range is synclinal, the peaks being of Paleozoic formation.
Building materials such as limestone, slate, granite, sands, and clay are abundant, and there are large deposits of marble of various hues. Bituminous coal is found along the eastern base of the mountains, and extensive beds of lignite exist in the east along the Missouri and Yellowstone rivers, while petroleum is also found. Copper is very abundant, and lead, iron, and silver ores also exist, the silver generally in conjunction with the copper: gold has been found in great quantities in many parts of the State. Around the headwaters of the Missouri and Yellowstone there are numerous hot springs and geysers.
Mining. The prosperity of Montana has been due largely to the development of its mineral resources. Within a radius of two miles of Butte City, $55,000,000 worth of copper, silver, and gold was mined in 1899. The copper output of the State for 1900 was 113,000 long tons, as against 268,000 for the whole United States, this being about 23 per cent. of the product of the world. The State stands second and is a close rival to Colorado in the production of silver. Since 1897 the output has had an annual commercial value of about $10,000,000. Silver, as also gold, is obtained from the same mines as copper. Montana ranks fifth as a gold-mining State, and its output has had an annual value of about $5,000,000 since 1897. Coal is being mined in increasing quantities, and almost reached $3,000,000 in value in 1900. The annual production of lead has stood at about 10,000 short tons since 1894. The mining of sapphires has begun recently; the stones found are of a superior quality, and are the most valuable of any of the precious stones mined in the United States.
Agriculture. In that part of the State lying west of the main range of the Rocky Mountains, the rainfall is generally sufficient for agricultural purposes. East of this range, however, the rainfall is, as a rule, inadequate, and purely agricultural pursuits can be carried on with profit only in those sections where irrigation is possible. The numerous streams supply an abundance of water which may be utilized for irrigation, and it is estimated that it will be possible to reclaim one-fifth of the total area of the State. Already considerable land has been brought under irrigation by the construction of numerous small temporary ditches; and large canals of a more permanent nature, and affecting more extensive areas, are being constructed. Of the 1,697,424 acres of improved land in 1900, exclusive of Indian reservations, 951,154 acres were irrigated, the latter area representing an increase during the last census decade of 171 per cent. The irrigated region is mainly in the southwest quarter of the State, the supply being obtained from the tributary headwaters of the Missouri and from the Yellowstone River. Farther east the depth of the channels, or the unfavorable conformation of the surface, as in the Bad Lands, greatly limits the irrigable area. The average cost per acre for the construction of ditches was the remarkably low figure of $4.92, which is due to the fact that the majority of the ditches are of private ownership, and without expensive dams and headgates. Large grazing areas are included in the farms of the State, and the average size of farms is therefore exceptionally large—885.9 acres for the entire State—but varying from 174 acres in Carbon County to 3093 in Yellowstone County.
The great development of the mining industry has created an excellent home market, and this
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