The map was the result of Wheeler's spectacular exploration of 1871. The sudden emergence of the Interior Department's civilian surveys posed a major threat to military mapping and exploration efforts. Wheeler, barely 30 years of age, was tasked to gather information and produce a highly accurate map of the area. This he accomplished and in so doing conceived of the U.S. Geographical Survey of which this map is the forerunner. Very detailed with scores of mining districts are located and named. Wheat refers to it as a "map of great interest." A most desirable sheet.

References: Wheat (TMW) #1237.

Condition: A

A little toning along fold and just a few spots, not distracting to the map.