In his Prefatory to Roughing It Mark Twain confessed, “Yes, take it all around, there is quite a good deal of information in the book.” These notes are intended to clarify and supplement this information by identifying people, places, and incidents, and by explaining literary allusions and topical references. In addition, they attempt to demonstrate the factuality of the narrative, so that the reader may more fully appreciate the artistry that Mark Twain used to shape his experiences into a work of literature.

The notes also identify portions of the text based on earlier printings—both of his own works that Mark Twain revised for inclusion in the book, and of works he quoted from other authors. Thus whenever mention is made that he incorporated into the text one of his pieces from, for example, the Buffalo Express or the Sacramento Union, the reader may find in Emendations of the Copy-Text and Rejected Substantives a record of the revisions he carried out while composing Roughing It. Likewise, when a note identifies the source of a quotation from the work of another author, the reader may find a record of any alterations Mark Twain is presumed to have made in the borrowed material.

All references in the text are keyed to this volume by page and line: for example, 1.1 means page 1, line 1. Chapter titles and picture captions are not included in the line count. Frequently cited works have been assigned an abbreviation, which in citations is followed by a page (or volume and page) number: “L2, 298” or “MTB, 1:337.” But most works are cited by the author’s last name (“Hunter, 254” or “Root and Connelley, 44”) or by a short title (“Tribute, 23”). When two or more works by the same author are cited in this way, the date of publication is used to distinguish them: “Fatout 1964, 80” and “Fatout 1976, 10.” Works by members of the Clemens family may be found under their initials: SLC, OC, and MEC. All abbreviations, authors, and short titles used in citations are fully defined in References. For the reader’s convenience, citations to works available in numerous editions may supply a chapter number (or its equivalent, such as a book or act number) rather than a page number. All quotations from holograph documents are transcribed verbatim from the originals (or photocopies thereof), even when a published form is also cited for the reader’s convenience. The location of every unique document or manuscript is identified by the standard Library of Congress abbreviation, or the last name of the owner, always defined in References.