This map was issued in the scarce, preliminary octavo edition of the Pacific Railroad Surveys that preceded the quarto edition by over a year. Wheat mentions the map on page 202 (volume four) under the much larger Gunnison & Beckwith map (TMW #842) that covers from St. Louis to San Francisco. On this smaller and earlier map, the central region of Colorado is several times more detailed. The route follows the Arkansas River valley to includes today's La Vita Pass, Garland, Gunnison and the vicinity of Grand Junction. The last camp is dated September 20th. Barely five weeks later Gunnison and Kern were killed near Siever Lake, Utah. Two additional maps are included: Sketch of the Northern Pacific Rail Road Exploration from St. Paul to Fort Union (31.5 x 18.0") and Sketch of the Progress of the Northern Pacific Rail Road Exploration Up to the crossing of the Shayen River (25 x 16.0"). The three maps are all bound into the back of the 118-page report.

References: cf. Wheat (TMW) #842.

Condition:

The Gunnison map and the "St. Paul to Fort Union" map are near fine with just a few tiny spots of foxing (A). The "Shayen River" map has some toning and faint offsetting (B). Text is mostly clean and bright with occasional minor foxing. Front cover and spine backstrip are missing and the remaining back cover is loose.