From 1821 to 1885 extends, in one form or another, the struggle for the last frontier. The imperative demands from the frontier are heard continually throughout the period, its leaders in long succession are filling the high places in national affairs, but the problem remains in its same territorial location. Connected with its phases appear the questions of the middle of the century. The destiny of the Indian tribes is suggested by the long line of contact and the impossibility of maintaining a savage and a civilized life together and at once. A call from the farther West leads to more thorough exploration of the lands beyond the great frontier, bringing into existence the continental trails, producing problems of long-distance government, and intensifying the troubles of the Indians. The final struggle for the control of the desert and the elimination of the frontier draws out the tracks of the Pacific railways, changes and reshapes the Indian policies again, and brings into existence, at the end of the period, the great West. But the struggle is one of half a century, repeating the events of all the earlier struggles, and ever more bitter as it is larger and more difficult. It summons the aid of the nation, as such, before it is concluded, but when it is ended the first era in American history has been closed.
A lengthening frontier made more difficult the maintenance of friendly relations between the two races involved in the struggle for the continent. It increased the area of danger by its extension, while its advance inland pushed the Indian tribes away from their old home lands, concentrating their numbers along its margin and thereby aggravating their situation. Colonial negotiations for lands as they were needed had been relatively easy, since the Indians and whites were nearly enough equal in strength to have a mutual respect for their agreements and a fear of violation. But the white population doubled itself every twenty-five years, while the Indians close enough to resist were never more than 300,000, and have remained near that figure or under it until to-day. The stronger race could afford to indulge the contempt that its superior civilization engendered, while its individual members along the line of contact became less orderly and governable as the years advanced. An increasing willingness to override on the part of the white governments and an increasing personal hatred and contempt on the part of individual pioneers, account easily for the danger to life along the frontier. The savage, at his best, was not responsive to the motives of civilization; at his worst, his injuries, real or imaginary,--and too often they were real,--made him the most dangerous of all the wild beasts that harassed the advancing frontier. The problem of his treatment vexed all the colonial governments and endured after the Revolution and the Constitution. It first approached a systematic policy in the years of Monroe and Adams and Jackson, but never attained form and shape until the ideal which it represented had been outlawed by the march of civilization into the West.