the centre, and 15 to 20 inches in the west, where it is insufficient for agriculture. The other parts of the State also suffer occasionally from drought. The soil in the greater part of the State is of excellent quality, and when sufficiently watered is rendered highly productive. In the east there is a subsoil of glacial till covered with a dark alluvial loam rich in nitrogen and again covered with many inches of black vegetable mold. A large part of the west has also a fine alluvial soil, but large areas here are stony and barren. The bottomlands of the Missouri and the terraced floors of its valley are very fertile. The State is as a whole a treeless prairie country. Forests are found only in the Black Hills above an altitude of 4000 feet, where there is a good growth of pine. Here and there along the river valleys there are more or less extensive groves of cottonwood, ash, elm, and maple.
Geology. Although the geological structure of the State is nearly homogeneous over the greater part of its area, there is nevertheless found represented every age from the Archæan to the Pleistocene except the Devonian. There are two Archæan nuclei, one in the east and one in the west. The former is a broad tongue of Sioux quartzite belonging to the Huronian system and extending westward to the James River from the neighborhood of Sioux Falls. To the north near Bigstone Lake is a smaller area of Laurentian granite. In the centre of the Black Hills is exposed the core of schists, slates, and granite. This is surrounded by narrow bands forming the denuded sections of the upturned Paleozoic strata, successively Potsdam sandstone of the Cambrian, Silurian limestone, and a broader band of Carboniferous limestone. Around this appear the sand and limestones, clays and marls of the Jura-Trias, and the whole is enveloped in the Cretaceous strata which cover four-fifths of the area of the State. The principal members are the Colorado marls, clays, and limestones covering nearly the whole of the eastern half, the Laramie formation occupying the northwestern quarter, and the Dakota sandstone underlying the valley of the James. The southwestern quarter of the State is covered with Miocene clays and conglomerates. Igneous rocks in the form of dikes of diabase and porphyry occur in both the eastern and western Archæan areas. The Pleistocene age is represented by the immense sheet of glacial drift covering the eastern half of the State to a line nearly coinciding with the Missouri River, and veiling the older formations. West of this line the Pleistocene deposits consist of aqueous drift.
Mining. The mineral wealth of the State appears chiefly in the Archæan area of the Black Hills, where there are more or less extensive deposits of copper, gold, silver, argentiferous lead, iron ores, manganese, nickel, tin, mica, and some graphite. The Triassic clays contain beds of gypsum, and beds of lignite as well as reservoirs of natural gas have recently been found. The Archæan and Paleozoic areas also yield a great variety of building and ornamental stone such as the red quartzite or jasper in the east. The Dakota sandstone of the James Valley is especially noticeable as a water-bearing stratum supplying powerful artesian wells. The mining activities consist mainly of quartz gold mining carried on in the southwest corner of the State. Difficulties in securing water have operated against the development of gold-mining, but elaborate and expensive schemes have been undertaken to secure adequate water supplies, and the output of gold is becoming larger. The value of the product increased from $4,006,400 in 1893 to $6,479,500 in 1901. The granite production in 1901 was valued at $99,941. Limestone and sandstone are also quarried. Portland cement was produced in 1900 to the value of $76,000, and clay products in the following year represented a value of $59,365.
Agriculture. Agriculture is almost wholly confined to the eastern half of the State. Facilities for irrigation are not extensive. In 1899, 43,676 acres were irrigated, principally from the tributaries of the Cheyenne River. In 1900, the total farm area was 19,070,616 acres, or 38.8 per cent. of the State's land area. Of the farm land 59.2 per cent. was improved, and about two-fifths of this amount was brought under improvement in the decade 1890-1900. South Dakota is one of the few States in which the size of farms is increasing, the average size in 1890 being 227.2 acres, and in 1900, 362.4 acres. In 1900, 3.4 per cent. of the farms were rented on the cash system, and 18.4 per cent. on shares. South Dakota is in the great wheat belt, and the cultivation of this crop has rapidly advanced until the State ranks among the first wheat States in the Union. The acreage in corn is also rapidly increasing, but the production of this crop is largely confined to the southeastern section. Oats are grown throughout the farming region, as is also barley, the latter crop being three times as great in 1900 as in 1890. The State stands third in the area devoted to flax. The acreage in hay and forage increased 47.1 per cent. in the decade 1890-1900. Potatoes are the principal vegetable grown. The following table embraces the leading crops:
| CROPS | 1900 | 1890 |
| Wheat | 3,984,659 | 2,259,846 |
| Corn | 1,196,381 | 753,309 |
| Oats | 691,167 | 580,289 |
| Barley | 299,510 | 97,370 |
| Rye | 39,253 | 9,229 |
| Flaxseed | 302,010 | 354,951 |
| Hay and forage | 2,287,875 | 1,554,913 |
| Potatoes | 33,567 | 35,440 |
Stock-Raising. The state has excellent grazing facilities. The number of cattle in 1900 was more than twice as great as in 1890, and there was a large increase in the number of horses, sheep, and swine, as shown in the following table:
| ANIMALS | 1900 | 1890 |
| Dairy cows | 270,634 | 210,240 |
| Other cattle | 1,276,166 | 477,679 |
| Horses | 480,768 | 250,305 |
| Mules and asses | 6,999 | 7,671 |
| Sheep | 507,338 | 238,448 |
| Swine | 823,120 | 590,465 |
Manufactures. Manufactures are limited mainly to neighborhood industries. In 1900, $7,578,895 was invested as capital and 3121 persons were engaged as wage-earners in the manufactures of the State.
Transportation. The railroads are confined to the region east of the Missouri River and to the mining region in the southwest corner, there
