The continental frontier, whose isolation the Union Pacific had threatened in 1869, was easily accessible by 1884. Along six different lines between New Orleans and St. Paul it had been made possible to cross the sometime American desert to the Pacific states. No longer could any portion of the republic be considered as beyond the reach of civilization. Instead of a waste that forbade national unity in its presence, a thousand plains stations beckoned for colonists, and through lines of railway iron bound the nation into an economic and political unit. "As the railroads overtook the successive lines of isolated frontier posts, and settlements spread out over country no longer requiring military protection," wrote General P. H. Sheridan in 1882, "the army vacated its temporary shelters and marched on into remote regions beyond, there to repeat and continue its pioneer work. In rear of the advancing line of troops the primitive 'dug-outs' and cabins of the frontiersmen, were steadily replaced by the tasteful houses, thrifty farms, neat villages, and busy towns of a people who knew how best to employ the vast resources of the great West. The civilization from the Atlantic is now reaching out toward that rapidly approaching it from the direction of the Pacific, the long intervening strip of territory, extending from the British possessions to Old Mexico, yearly growing narrower; finally the dividing lines will entirely disappear and the mingling settlements absorb the remnants of the once powerful Indian nations who, fifteen years ago, vainly attempted to forbid the destined progress of the age." The deluge of population realized by Sheridan, and let in by the railways, had, by 1890, blotted the uninhabited frontier off the map. Local spots yet remained unpeopled, but the census of 1890 revealed no clear division between the unsettled West and the rest of the United States.