The first edition of Mitchell's atlas map of the United States.
This map illustrates the evolving territorial borders of the Trans-Mississippi West. New Mexico Territory extends from California to Texas, although Arizona is noted along the Mexico border, in what would come to be known as the Baylor Line (Gadsden Purchase of 1854 is also noted). Nebraska runs from Kansas to Canada and the Rocky Mountains to the Missouri (pre-dating massive Dacotah Territory which was depicted the following year when Nebraska Territory was significantly reduced), and includes all of Montana, Wyoming and part of Colorado.
Washington Territory wraps around Oregon, incorporating much of modern day Idaho, and includes to the Great South Pass, an even larger treatment than the following year, when the boundary of Washington Territory is truncated to the west of the Pass. Kansas runs from Missouri to the Rocky Mountains, including a portion of Colorado on the Eastern Slope of the Rocky Mountains, one year after the start of the Colorado Gold Rush.
A massive Utah Territory appears, extending from the Rocky Mountains to California and incorporating much of modern day Colorado and all of Nevada. No sign of Colorado, which would appear the following year as a Territory. The map shows early explorers routes, forts, Indians, railroads, towns, rivers, mountains, etc., and is rich with topographical and historical information. Inset of Newfoundland.
Samuel Augustus Mitchell Jr. inherited the Mitchell Company from his father in 1860. For over thirty years, the company had specialized in the production of school atlases and wall maps of America. They were one of the pioneers on engraving on steel plates. In 1860, Samuel Jr. released the New General Atlas, which had been compiled in house and replaced a previous atlas by Tanner. The elder Mitchell died in 1868 and Samuel Jr. continued the business until the 1890s. At its height, the Mitchell Company employed 250 people and sold 400,000 publications annually.