384 THE GROWTH OF THE UNITED STATES 



are lacking, but since 1850 wealth has increased more rapidly 

 than an}'- 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. 



