Detailed topographical map of a part of California, centered on the Merced River and Tuolomne River, including Yosemite Valley, Hetch Hetch Valley and Sequoia National Park.
In 1866, Joseph S. Wilson, the Commissioner of the General Land Office, assessed the mineral resources of the US and opined the proper development was a matter of the highest concern to the American people. On March 2, 1867, Congress authorized the first western explorations in which geology would be the principal objective: a study of the geology and natural resources along the fortieth parallel route of the transcontinental railroad, under the Corps of Engineers, and a geological survey of the natural resources of the new State of Nebraska, under the direction of the General Land Office.
Four major surveys resulted, generally referred to by their leaders on the ground, King, Hayden, Powell and Wheeler. In 1869, Lieutenant George Wheeler was Engineer Officer on the staff of the Commanding General of the Army's Department of California (which covered California, Nevada, and Arizona). Wheeler, then only 26, had graduated sixth in his class from West Point in 1866. In early June 1869, Lieutenant Wheeler was ordered to organize and equip a party to explore the country south and east of White Pine, Nevada, as far as the head of navigation on the Colorado, to obtain data for a military map and to survey the possibility of a wagon road and select sites for military posts. In 1871, the Engineers sent Lt. Wheeler to explore and map the area south of the Central Pacific Railroad in eastern Nevada and Arizona. On his return from the 1871 expedition, Wheeler, convinced that the day of the pathfinder had ended, proposed a plan for mapping the United States west of the 100th meridian on a scale of 8 miles to the inch, expected to cost $2.5 million and take 15 years. Congress authorized the program on June 10, 1872.
The surveys continued throughout the 1870s. This map comes from the Topographical Atlas Projected To Illustrate United States Geographical Surveys West Of The 100th Meridian Of Longitude Prosecuted In Accordance With Acts Of Congress Under The Authority Of The Honorable The Secretary Of War, And The Direction Of Brig. Genl. A.A. Humphreys, Chief Of Engineers, U.S. Army. Embracing Results Of the Different Expeditions Under The Command Of 1st Lieut. Geo. M. Wheeler, Corps Of Engineers. Julius Bien, lith.