During the 1850s, the U.S. government sponsored an extensive series of expeditions designed to gather information on the vast new territories that had been acquired in western North America. The discovery of gold in California further stimulated westward traffic and heightened the need for a faster and more convenient way to bring the far-flung parts of the country together. In 1853 Congress commissioned the Army's Topographic Bureau to conduct a series of surveys to find a suitable route for a transcontinental railroad. There were six major expeditions; five of them covered the area between the Great Plains and west coast, and the sixth explored the coastal states of California and Oregon. All of these expeditions were accompanied by naturalists and artists to document the landscape, flora and fauna along the route. The reports, maps and lithographs were published in the 13 volume report "Explorations and Surveys to ascertain the most practicable and economical route for a Railroad from the Mississippi river to the Pacific Ocean."

The entire state is shown with the portion from the Gold Region and San Francisco hand colored to reflect geological knowledge. These regions are color coded to a legend at the left side of the map detailing nine different geological zones. A nice, early and colorful map of California with a fair amount of geographical detail. Shows many interesting details throughout, and especially along the American River. Lake Tahoe is not shown, rather there is a very small lake named Lake Bonpland.

References: Marcou & Marcou #678.

Condition: B

Folding, as issued. A few areas of foxing, mostly along folds, else very good with fine coloring.