When the last frontier had vanished, it was seen that men of this American stock had penetrated into every valley, traversed every plain, and explored every mountain pass from Atlantic to Pacific.  They organized every territory and prepared each for statehood.  It was the enterprise of these sons and grandsons and great-grandsons of the Revolutionary Americans, obeying the restless impulse of a pioneer race, who spread a network of settlements and outposts over the entire land and prepared it for the immigrant invasion from Europe.  Owing to this influx of foreigners, the American stock has become mingled with other strains, especially those from Great Britain.

The Census Bureau estimated that in 1900 there were living in the United States approximately thirty-five million white people who were descended from persons enumerated in 1790.  If these thirty-five million were distributed by nationality according to the proportions estimated for 1790, the result would appear as follows: 

English    28,735,000
Scotch      2,450,000
Irish         665,000
Dutch         875,000
French        210,000
German      1,960,000
All others    105,000

In 1900 there were also thirty-two million descendants of white persons who had come to the United States after the First Census, yet of these over twenty million were either foreign born or the children of persons born abroad.  If this ratio of increase remained the same, the American stock would apparently maintain its own, even in the midst of twentieth century immigration.  But the birth rate of the foreign stock, especially among the recent comers, is much higher than of the native American stock.  Conditions have so changed that, according to the Census, the American people “have concluded that they are only about one-half as well able to rear children—­at any rate, without personal sacrifice—­under the conditions prevailing in 1900 as their predecessors proved themselves to be under the conditions which prevailed in 1790.”

The difficulty of ascertaining ethnic influences increases immeasurably when we pass from the physical to the mental realm.  There are subtle interplays of delicate forces and reactions from environment which no one can measure.  Leadership nevertheless is the gift of but few races; and in the United States eminence in business, in statecraft, in letters and learning can with singular directness be traced in a preponderating proportion to this American stock.

In 1891 Henry Cabot Lodge published an essay on The Distribution of Ability in the United States,[6] based upon the 15,514 names in Appleton’s Cyclopedia of American Biography (1887).  He “treated as immigrants all persons who came to the United States after the adoption of the Constitution,” and on this division he found 14,243 “Americans” and 1271 “immigrants” distributed racially as follows: 

AMERICANS IMMIGRANTS