At the time when Pike first appeared in print, it was the fashion to regard an index to a book rather as an elegant superfluity, or a luxury of leisurely authorship, than as the imperative obligation and absolute necessity which we now find it to be, whenever anything else than fiction or poetry becomes a candidate for public favor. Pike has never been indexed before; and many who now see how lengthy is the list of proper names of persons, places, and other things, may for the first time become aware of the extent and variety of information of which this author's work has proved to be either the prolific source or the pregnant occasion. All of the plates which illustrated the original edition of Pike have been reproduced in facsimile. They consist of a portrait of the author and six maps. To these are now added a facsimile of an autograph letter, and a new map, both prepared expressly for the present edition. The letter requires no further remark than that it is believed to be the first one ever published, and that it is also printed in its proper connection in the text of my Memoir, with many other hitherto unpublished documents. The new map, which I have legended as a Historico-geographical Chart of the Upper Mississippi River, has been compiled and drawn under my direction by Mr. Daniel W. Cronin, a skillful draughtsman of the U. S. Geological Survey, and is copyrighted by my publisher. It is based primarily upon the Map of the Mississippi River from Lake Itasca to the Falls of St. Anthony, compiled from surveys and reconnoissances made under the direction of Major F. U. Farquhar and Captain Charles J. Allen, U. S. A., and from the U. S. Land Surveys, published in fifteen sheets, on the scale of inch to mile, by the Engineer Department of the Army, in 1881. The hydrographic data from this source are supplemented from the latest map of Minnesota published by the U. S. General Land Office, from the sectional maps of Minnesota and of the Upper Mississippi lately issued by Jewett and Son of St. Paul, and from various other sources, in protracting the branches of the main stream and locating the lakes, etc., beyond the area shown on the Engineer charts. The Jewett maps are the best ones I have seen among those published by private enterprise; the map of Minnesota for which a certain Chicago firm is responsible is the worst of all those which have appeared of late years. My corner-map of the Infant Mississippi or "Cradled Hercules," on a much larger scale than the rest, is reduced from Brower's map of the Itasca State Park, with the author's kind permission; the names given to the numerous features of the Itascan source of the Mississippi are those now officially recognized, with the addition of a few which I have myself bestowed in the course of my notes on Pike, among other results of my recent tour of observation. In lettering the main part of this chart, my idea was, first, to illustrate Pike, by