Being the most accurate map to date of the region of the Arizona and New Mexico Territories purchased by the United States in 1854, along with portions of Texas, Sonora, and Chihuahua. This map was prepared using the most accurate survey methods. In comparisons to maps prepared by the US Army it has been found superior in all regards. It is published as a set of onionskin overlays to allow the user to explore the geography of the region in the manner which most suits their needs.