Two important maps of the Transmississippi West by G. J. Warren, including an annotated proof copy of his seminal 'Map of the Territory of the United States from the Mississippi to the Pacific Ocean
.' William H. Goetzmann describes this map as the "most important achievement of the [Pacific Railroad Surveys]. … An event comparable in importance to the publication of Lewis and Clark’s first reports, Warren’s map marked the culmination of six decades of effort to comprehend the outlines of western geography. Though there were still vast areas marked unexplored on its surface and not all of the features were correctly laid down, Warren’s map, nevertheless, was a landmark in American cartography …. Compared to Warren’s map, all previous works of a general nature on the trans-Mississippi West are mere sketches …. The map was of fundamental importance in the progress of geographical knowledge in the United States" ('Army Exploration in the American West 1803–1863,' pp. 333–337).
This copy is a proof before publication with two autograph revisions by Warren and his signed annotation, "Proof sheet from an unfinished engraving | Feb. 22. 1858 | G. K. Warren | Sr. Top Engr." In one revision, Warren has deleted the names of Indian peoples believed to be present in the Colorado and Green rivers area of the Southwest and instead marked that area "unexplored." In the other, he has extended the Salmon River southward.
The second map is an early precursor to Warren's great map, described by him in a Note appearing under the title as "a hurried compilation of all the authentic surveys and is designed to exhibit the relations of the different routes to each other; the topography represents only those great divides which form summits on the profiles of the routes."