Sheet VI of the monumental Preuss-Fremont map, the first map "to show the Oregon Trail accurately" (Rumsey).
This sheet of the map crosses most of Southern Idaho, extending from Fort Hall, Idaho, 100 miles north of Salt Lake to Fort Boise, Idaho, tracking the course of the Lewis Fork of the Columbia, also known as the Snake River.
Reese describes the map as "One of the greatest monuments to the cartography of the American West."
Charles Preuss was the cartographer on John Fremont's first and second expeditions and drew all of the maps which accompany Fremont's reports. Preuss also produced this highly important map of the Oregon Trail. Drawn at a scale of ten miles to an inch, the map provides remarkably accurate cartographical information about the whole of the 1,670 mile route between the Missouri River and the Columbia River.
Preuss's seven sheet map provides a close look at the daily progress of the Fremont Expedition, from June 10, 1842, to October 26, 1843, showing the location of each overnight camp, where each noon-day halt was called, and the total distance from the starting point of Westport Landing. Longitudinal and latitudinal coordinates are also given, as are daily "Meteorological Observations" and "Remarks," including notes on the availability of game, water, grazing, the friendliness (or otherwise) of local Indian Tribes, and some quite lengthy extracts from Fremont's Report. A second revised issue of this map was published in 1849.
As noted by Wheat:
More than any other persons, John Charles Fremont and Charles Preuss dominate the cartography of the American West during the three years before the gold rush...Owing to its rarity and to its long having stood in the shadow of the more widely known and distributed Fremont-Preuss map of 1845, Preuss' sectional map of 1846 has been insufficiently appreciated by students of Western history. In particular, those interested either in Fremont's travels in 1842-43 or the revolution of the transcontinental wagon roads will find that the map rewards close study.
The present example is the second edition, published three years after the separately issued first edition, in John A. Rockwell's Report . . . survey of certain routes for a canal or railroad between the Atlantic and Pacific Oceans; also... the establishment of a national road from the western frontier of Arkansas to California. . . . This edition of the map is identical to the original 1846 Senate issue, except that it does not have the Baltimore lithographer's name (E. Weber), and Sheet VI was misnumbered (though here corrected).
An essential map for Western collectors.