Detailed map of the Southwest, prepared at the outset of the Surveys West of the100th Meridian.

The map is one of the few maps executed by Louis Nell during this time working for the War Department Topographical Engineers. Nell would later settle in Denver and become the most important map maker in Colorado from 1880 to the early 20th Century.

This complete report describes Wheeler's explorations in Nevada and Arizona and the first exploration of Death Valley. The report includes a large folding Preliminary Topographical Map, covering parts of Southern California, Nevada and Arizona and details scores of mining districts. Wheat refers to it as a "map of great interest."

Wheeler notes that the map "is a hasty and partial compilation from the topographical data already received, many still remaining en route." The report contains a great amount of information on the mining districts, as well as information concerning the Indians, military sites, routes for roads, and grazing lands.