This section is from the book "Principles Of Sociology With Educational Applications", by Frederick R. Clow. Also available from Amazon: Principles of sociology with educational applications.
The social organization of any people varies radically according to the density of the population. Human beings, like any other form of life, tend to multiply up to the limit of the food supply and the other means of subsistence which are under their control. During a time of transition, as when a civilized people is taking possession of a country previously occupied by savages, the population may be small in comparison with the means of subsistence. But population will double every generation when circumstances are favorable, and so genetic increase alone will in time cause it to press upon the limits. Unused resources are also a powerful attraction to immigration. It is possible, therefore, for a newly opened region to become well occupied in even less than a generation. For example, Mexico ceded California in 1848 with a very sparse population. Gold was discovered there that same year, and immigration began at once. California became a state in 1850 with a population of 92,597, and in 1860 the population was 379,994. In 1859 silver was found in the territory of Utah. Again population followed, this time from the west as well as from the east. The district thus settled was set off as the territory of Nevada in 1861, and admitted as a state in 1864. Oklahoma is a more recent example of a new state made in less than a generation.
The way the population is arranged on the land depends on the character of the industries. Agriculture is the only industry which tends to disperse the population at all evenly. The other extractive industries mass it at the points most accessible to the resources. A mine in a newly settled country means a town set in a wilderness. Manufacturing, when not subsidiary to agriculture, gathers the population into cities of moderate size. The cities of metropolitan size are formed by commerce.
Density of population depends on the quantity of food produced. The beginnings of social evolution . . . are always to be found in a bountiful environment. Moreover, density of population follows abundance of food, whether the supplies are obtained from the soil directly, or indirectly, in exchange for manufactures: and other things being equal, the activity and the progress of society depend, within limits, on the density of the population.
A sparse population, scattered over a poor soil, can carry on production only by primitive methods and on a small scale. It can have only the most rudimentary division of labor; it cannot have manufacturing industries, or good roads, or a rapid interchange of intelligence; all of which, together with a highly developed industrial organization and a perfect utilization of capital, are possible to the populations that are relatively dense.
A highly developed political life, too, is found only where population is compact. Civil liberty means discussion, and discussion is dependent on the frequent meeting of considerable bodies of men who have varied interests and who look at life from different points of view. Movements for the increase of popular freedom have usually started in towns. The American Revolution and the anti-slavery agitation were as peculiarly products of town life as are socialism, nationalism, and the single tax agitation to-day.
Education, religion, art, science, and literature are all dependent on a certain density of population. Schools, universities, churches, the daily newspaper, great publishing houses, libraries, and museums come only when the population per square mile is expressed by more than one unit, and their decay is one of the first symptoms that population is declining. Long before the desertion of the country villages in several of our eastern states had begun to attract the attention of economists, the decline of the schools and the churches was observed with solicitude by educators and by the religious press. - Giddings, Principles of Sociology, pp. 366, 367.