But it was not until after the Civil War that the progress of events dealt its heaviest blow at the policy of Indian seclusion. In 1867-8 the great plough of industrial civilization drew its deep furrow across the continent, from the Missouri to the Pacific, as a sign of dissolution to the immemorial possessors of the soil. Already the Pacific Railroad has brought changes which, without it, might have been delayed for half a century. Not only has the line of settlement been made continuous from Omaha to Sacramento, so far as the character of the soil will permit; but from a score of points upon the railroad population has gone north and gone south, following up the courses of the streams, and searching out every trace of gold upon the mountains, till recesses have been penetrated which five years ago were scarcely known to trappers and guides, and lodgement has been effected upon many even of the more remote reservations. The natural effects of this introduction by the railroad of white population into the Indian country have not yet been wholly wrought. There are still reservations where the seclusion of the Indians is practically maintained by the ill-repressed hostility of tribes; some, where the same result is secured by the barrenness or inaccessibility of the regions in which they are situated; but it is evident that the lapse of another such five years will find every reservation between the Mississippi River and the Rocky Mountains surrounded, and to a degree penetrated, by prospectors and pioneers, miners, ranchmen, or traders. Against the intrusion of these classes, in the numbers in which they are now appearing in the Indian country, the Intercourse Act of 1834 is wholly ineffective. It was an admirable weapon against the single intruder: it avails nothing against the lawless combinations of squatter territories. While the movements of population have thus in great part destroyed, and threaten soon utterly to destroy, at once the seclusion in which it was hoped the native tribes might find opportunity for the development of their better qualities, and the natural resources to which, in the long interval that must precede the achievement of true industrial independence by a people taught through centuries of barbarous traditions to despise labor, the Indian might look for subsistence, Congress in 1871 struck the severest blow that remained to be given to the Indian policy, in its fourth great feature,--that of the self-government of tribes according to their own laws and customs,--by declaring that "Hereafter no Indian nation or tribe within the territory of the United States shall be acknowledged or recognized as an independent nation, tribe, or power, with whom the United States may contract by treaty."