In republishing these essays in collected form, it has seemed best to issue them as they were originally printed, with the exception of a few slight corrections of slips in the text and with the omission of occasional duplication of language in the different essays. A considerable part of whatever value they may possess arises from the fact that they are commentaries in different periods on the central theme of the influence of the frontier in American history. ...] Collection of essays dealing with the significance of the concept of frontier in American history and its influence on it. Originally published in 1920.