New states in plains and mountains marked the abolition of the last frontier as they had the earlier. In less than ten years the gap between Minnesota and Oregon was filled in: North Dakota and South Dakota, Montana, Idaho, Wyoming, and Washington. In 1890, for the first time, a solid band of states connected the Atlantic and Pacific. Farther south, the Indian Country succumbed to the new pressure. The Dawes bill released a fertile acreage to be distributed to the land hungry who had banked up around the borders of Kansas, Arkansas, and Texas. Oklahoma, as a territory, appeared in 1890, while in eighteen more years, swallowing up the whole Indian Country, it had taken its place as a member of the Union. Between the northern tier of states and Oklahoma, the middle West had grown as well. Kansas, Nebraska, and Colorado, the last creating eleven new counties in its eastern third in 1889, had seen their population densify under the stimulus of easy transportation. Much of the settlement had been premature, inviting failure, as populism later showed, but it left no area in the United States unreclaimed, inaccessible, and large enough to be regarded as a national frontier. The last frontier, the same that Long had described as the American Desert in 1820, had been won. NOTE ON THE SOURCES The fundamental ideas upon which all recent careful work in western history has been based were first stated by Frederick J. Turner, in his paper on _The Significance of the Frontier in American History_, in the _Annual Report of the Am. Hist. Assn._, 1893. No comprehensive history of the trans-Mississippi West has yet appeared; Randall Parrish, _The Great Plains_ (2d ed., Chicago, 1907), is at best only a brief and superficial sketch; the histories of the several far western states by Hubert Howe Bancroft remain the most useful collection of secondary materials upon the subject. R. G. Thwaites, _Rocky Mountain Exploration_ (N.Y., 1904); O. P. Austin, _Steps in the Expansion of our Territory_ (N.Y., 1903); H. Gannett, _Boundaries of the United States and of the Several States and Territories_ (_Bulletin of the U.S. Geological Survey_, No. 226, 1904); and _Organic Acts for the Territories of the United States with Notes thereon_ (56th Cong., 1st sess., Sen. Doc. 148), are also of use.