ful. The average temperature is low, but there may be periods of intense heat and intense cold, the extreme recorded temperatures being 116° and 44° below zero. The mean temperature for January is 18.1° for Sheridan, in the north, and 25.1° for Cheyenne, in the southeast. For July the mean is about 67° in both localities. In most years the maximum rises above 100°, and the minimum falls more than 30° below zero. The winters, though very cold, are not exceedingly severe, as the snowfall is light, and the dry air makes the cold easily endurable. The average annual precipitation for the State is 13 inches, and the records of the various local stations do not vary much from this figure. The largest amount of rain falls between March and June, but irrigation is everywhere necessary, though the mountain ranges receive sufficient rain to feed the numerous streams and support forests. The soil is generally a light sandy loam, becoming darker and richer in the river valleys. In the arid Red Desert region the soil over large areas is strongly impregnated with saline matter and poor in humus, so that even the common sagebrush (Artemisia) gives place to the salt sage (Atriplex) and greasewood. For other details of flora and for fauna, see Rocky Mountains.
Geology and Mineral Resources. The Medicine Bow, Laramie, Big Horn, and Wind River ranges have their cores of Archæan crystalline rocks exposed along their crests. These outcrops are flanked by narrow bands representing the upturned edges of Paleozoic and Lower Mesozoic strata in a regular series from Cambro-Silurian to Jura-Trias. On the latter rest the Cretaceous strata, which form the surface rock of the Cheyenne, Powder River, Wind River, and Laramie basins. The southwestern plains and the Big Horn Basin are covered with Eocene deposits, and the southern part of the Platte Basin, east of the Laramie range, is covered with the later Tertiary deposits of the Great Plains formation. The Yellowstone region, in the northwest, is volcanic, and consists largely of lava flows. The mineral wealth of Wyoming is very extensive and varied, and gives promise of great future development. Copper and lead ores associated with silver exist in every range, and gold is also found in numerous localities. Red hematite iron ores are deposited on the southeastern slope of the Laramie range, but the most important mineral at present is coal, of which there are a number of large fields, chiefly in the southwestern part of the State. Each field contains several workable veins ranging from pure lignite to good bituminous, and in some localities even to a semi-anthracite. Great bands of bituminous shale exist in the Green River Valley; and in the central part of the State, as well as in several other localities, there are a number of petroleum and natural gas fields, some of which come naturally to the surface as petroleum springs. Large veins of graphite and some asphaltum deposits occur in the oil region. Other minerals are asbestos and gypsum, the latter occurring in great quantities, while building stones exist in immense variety and inexhaustible amounts.
Mining. Mining, thus far, has been limited principally to the production of coal. The output of this mineral increased almost steadily from 6925 short tons in 1868 to 1,170,318 in 1887, and 4,485,374 in 1901. In the last year the output was valued at $6,060,462. Sweetwater and Unita counties lead in coal production. In 1901 Wyoming ranked twelfth among the coal-mining States. The coal resources of the State are enormous and give promise of playing an important part in the future development of the State. The numerous oil-fields have begun to be worked. In 1901, 5400 barrels of crude petroleum were obtained, valued at $37,800. In the central part of the State a lubricating oil of superior quality is produced. Lack of transportation facilities has prevented any extensive development in this field.
Agriculture and Stock-Raising. Wyoming is one of the most arid States in the Union, and practically no crops can be grown without irrigation. The agricultural land of the State, as a whole, lies at a greater altitude than that of any other State, and the character of agriculture, methods, and products is governed by this fact. The industry was for a long time confined to grains, and this is still of importance. It is estimated that nearly one-half of the total area of the State is adapted to grazing. In the census year 1900, 18.4 per cent. of the gross income of agriculture was accredited to the stock-raising industry. The native grasses are cured naturally by the dry climate. Some difficulty is incurred in the industry, however, because of the severity of the winters. Wyoming in 1900 had 5,541,412 sheep, including lambs. This was more than twice as many as were reported for any other State. The sheep are pastured in the mountains during the summertime, and are then removed to the plains, where they find sustenance during the winter months. It will be seen from the table appended that sheep-raising has developed mainly since 1890. The breed of sheep is of superior quality, the average yield being greater than it is for any other Western State. The average yield of fleeces increased from 7.0 pounds in 1890 to 8.2 in 1900. Cattle-raising is also very important. Wyoming also produces a hardy stock of horses and annually sends considerable numbers to Eastern markets. The large recent development in stock-raising is a result of the growth of the irrigation system, and in no other State is irrigation so intimately related with grazing. Of the 435,862 acres in crops in 1899, 402,099 were irrigated and 90 per cent. of this devoted to hay and forage. The water supply of the State is good, the melting snow of the mountains supplying numerous perennial streams with currents of considerable volume. The irrigated land is well distributed over the State, but over half of the total is in the valley of the North Platte River. In 1900, 8,124,536 acres were included in farms, and 792,332 acres were improved. With the construction of adequate transportation facilities and the creation of a home market through the development of the mining industry, this territory will be brought rapidly into cultivation. The hay crop consists of alfalfa, timothy, and other ‘tame’ varieties and also the native grasses. The climate is too severe for corn, but oats and wheat grow abundantly. Potatoes are a favorite crop. The hardier fruits and vegetables are successfully raised. The following table shows the number of domestic animals on farms and ranches and the acreage of the leading crops:
