THE REGIONS OF THE UNITED STATES extraordinary diversity of geographic con ditions in the United States is accompanied by a sur prising uniformity of economic opportunity and social conditions and a similarity of culture has often been commented upon. Russia, for instance, is the only nation which compares with the United States in the variety and extent of agricultural regions. Dr. Oliver E. Baker 1 has traced our unity of culture amid diversity of environments to three factors: (1) the strong pressure of economic competition, (2) the facilities for the dissemina tion of new ideas, (3) and the mobility of capital and labor. "I suppose," writes Professor E. A. Ross, "no large population shows so faint and doubtful a response to region as we Americans. Never before were folk of forest or valley, of sea or river delta, so little insulated. Our education, reading matter, films, sports, standard ized articles of consumption, religious denominations, trade and professional unions, political parties and com mon institutions pull us into a national or at least a sec tional plane." E Frederick Jackson Turner sees in the cultural homogeneity of the United States a lack of the historical attitudes of Europe. "There are not in the United States," he writes, "the historic memories of so many national wrongs and wars. . . . There is not here the variety of languages nor races nor the sharp con trasts in cultural types ; there has not been the same bitterness of class conflicts ; nor the same pressure of economic need, inducing the various regions to seek by arms to acquire the means of subsistence, the control of natural resources." 3 It is in the traits of her urban-industrial culture that America is most homogeneous ; in her rural life she dis plays more diversity. Possibly the most satisfactory classification of the natural regions of the United States is that worked out by Dr. Oliver E. To him an agricultural region is a large area of land characterized by a homogeneity in crops grown but sufficiently unlike adjacent areas to be noticeable. The economic culture
of certain plants and consequently the agricultural re gions are dependent upon the following physical con ditions: 1. Moisture conditions, rainfall, and rate of evaporation.
2. Temperature conditions, length of growing season.
3. Topography, contour of the land.
4. Soils, physical, chemical, and bacteriological factors.' In regard to climatic factors the United States falls roughly into four areas : a cold northern, a warm south ern, a moist eastern, and a dry western region.' In regard to soils there are three main regions : the central plains, largely dark-soiled grasslands ; the East and South, largely light-colored forest lands ; and the western arid lands.' In addition to physical factors, W. J. Spillman 8 sees biological and economic factors as determining plant regions. Bacterial content 61 soils, the preference of al falfa for alkaline soils, and the relation of soils and cli mates to insect pests and fungous diseases he classifies as biological. Under economic factors determining plant production are the value per unit of weight, and the distance to market.
The main plants affected by these various factors are corn, wheat, cotton, oats, and hay. Together they nor mally occupy more than 30,000,000 acres apiece on American farms, taking more than 87 per cent of the total crop area of the country.' In combination with live stock they make up the various types of farming. Be ginning with the South, Dr. Baker lists the following agricultural regions of the eastern part of the United States : 1. Subtropical Crops Belt.
2. Cotton Belt.
3. Middle Atlantic Trucking Region.
4. Corn and Winter Wheat Belt.
C. Corn Belt.
6. Hay and Dairying Belt.
7. Spring Wheat Area.' The western United States he divides according to crops produced into the following areas : 8. Grazing and Irrigated Crops Region.
9. Columbia Plateau Region.
10. Pacific Subtropic Crops Region.