National Geographic : 1898 Sep
384 THE GROWTH OF THE UNITED STATES are lacking, but since 1850 wealth has increased more rapidly than any other measurable factor in national progress, as illus trated by the remaining curves in the diagram. In the last half century the population of the United States has more than tripled, yet the wealth has more than thrice tripled, and the per capita wealth of the American citizen has risen far above the corresponding value for the other countries. This element of growth, too, is correlated with the increase in area, especially the epochal accession of half a century ago; for, although the statistics are wanting for the first half of the century, mere in spection of the later curves shows that the rate of increase must have been at least doubled or tripled almost immediately after the acquisition of Texas and California. On reviewing the factors of national development, it becomes clear that territorial expansion, great as it has been, is not the principal one; for population has increased much more rapidly than area, while wealth (a partial expression of individual enter prise) has increased three times more rapidly than population it becomes clear that American progress resides in the conquest of nature rather than in conquest of nations. Yet it is equally clear that every territorial accession gave new opportunity for growing enterprise, and was soon followed by new industries, new associations, new lines of thought, all contributing to in creased individual wealth and augmented national strength. It is no less clear that the character of the territorial accession has shaped the character of the consequent progress: The Louisiana purchase created a demand for navigation of the Mississippi and its tributaries; the demand was met by the native genius which is always with us, and the finest steam-packet system in the world was developed to meet it. The conquest of California created a demand for transportation facilities; it was met by the development of the American railway system. The pushing of population into the arid districts created a demand for irriga tion; it has been met by the development of irrigation engineer ing, irrigation laws, and other features of an irrigation system which marks an era in national history. On the whole it seems clear that the several factors of development are interrelated in a manner so natural and necessary as to produce that normal growth so conspicuous in the history of the United States; that the rapid territorial expansion of early decades was not too rapid for assimilation in the national structure, yet was rapid enough to meet national needs.