John C. Frémont and Charles Preuss’s landmark map of 1848.
This map has been accorded two-fold importance in the development of the westward expansion: first, as a major contribution to geographical and cartographical knowledge, and secondly, as historical documentation of Frémont’s third expedition. The map is a remarkable graphic depiction of this expedition and is considered one of the most important 19th century American maps. It covers all of the western territories from the 105th Meridian. Among the most interesting features are the appearance of the term Golden Gate at the entrance to the Bay of San Francisco, the markings of the El Dorado or Gold Region in the California Gold Fields, a hypothetical east-west mountain range near the 42nd parallel, and a notation identifying the location of Mormon settlements for the first time. Wheat illustrates the map and devotes eight pages to its description.
Having been court-marshaled and dismissed from the Army in 1847, Frémont was not asked to publish the details of this last expedition by the Corps of Topographical Engineers as would normally be required. Instead, the Geographical Memoir comprised his report. It was published nonetheless by Congress at the behest of the powerful Senator Benton. The memoir is also known as Misc. Doc. No. 148, 30th Congress, 1st Session. This is the large, and increasingly rare, map from that report.