As to dates, we shall need but few. Indeed, it will suffice if the reader shall remember but one date out of all given in this book—that when it became no longer profitable to trap the beaver in the West. This date, remembered and understood logically, may prove of considerable service in the study of the movements of the American people. As to the apparently disconnected nature of the studies here presented, it is matter, as one may again indicate, not of accident. On the contrary, the arrangement of the material is thought to constitute the chief claim of the work for a tolerant consideration. I shall ask my reader to consider the movements of the American population as grouped under four great epochs. There was a time when the west-bound men were crossing the Alleghanies; a time when they crossed the Mississippi; a time when they crossed the Rocky Mountains. Now they cross the Pacific Ocean. Roughly coincident with these great epochs we may consider, first, the period of down-stream transportation; second, of up-stream transportation; and lastly, of transportation not parallel to the great watercourses, but directly across them on the way to the West. These latter groupings were employed in a series of articles printed in the Century Magazine in the year 1901-1902, the use of this material herein being by courtesy of the Century Company. I have not hesitated to employ the medium of biography where that seemed the best vehicle for conveying the idea of a great and daring people led by a few great and daring pilots, prophets of adventurings: hence the sketches of the lives of the great frontiersmen, Boone, Crockett, and Carson,—all great and significant lives, whose story is useful in illustrative quality. I am indebted for many facts obtained from special study by Mr. Horace Kephart, an authority on early Western history, illustrating thoroughly the part that the state of Pennsylvania played in the movement of the early west-bound population. Mr. Warren S. Ely, a resident of historic Bucks County, Pennsylvania, supplements Mr. Kephart’s material with results of local investigations of his own. Mr. Alexander Hynds of Tennessee assists in telling the story of that Frontier Republic whose history blends itself so closely with Western affairs of a hundred years ago. I have quoted freely from Mr. N. P. Langford, a man of the early trans-Missouri, an Argonaut of the Rockies, who has placed at my disposal much valuable material. Mr. Hiram M. Chittenden’s splendid work on the history of the American fur trade has proved of great value. I am indebted to many books and periodicals for data regarding the modern American industrial development. I am indebted also to many early authors who wrote of the old West, and am under obligations to very many unknown friends, the unnamed but able writers of the daily press.