The Last American Frontier by Frederic L. Paxson

I have told here the story of the last frontier within the United States, trying at once to preserve the picturesque atmosphere which has given to the "Far West" a definite and well-understood meaning, and to indicate those forces which have shaped the history of the country beyond the Mississippi. In doing it I have had to rely largely upon my own investigations among sources little used and relatively inaccessible. The exact citations of authority, with which I might have crowded my pages, would have been out of place in a book not primarily intended for the use of scholars. But I hope, before many years, to exploit in a larger and more elaborate form the mass of detailed information upon which this sketch is based.