United States Geological Exploration of the Fortieth Parallel (1867-1881)

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The U.S. Geological Exploration of the Fortieth Parallel took place over five seasons, traveling through California, Nevada, Utah, and Colorado to map its topography, and discover its resources during the years 1867 – 1881. Commissioned by Congress, and placed under the control of the United States Engineer Corps, geologist Clarence R. King, was selected as the leader of the exploration. King was entrusted with the first major effort to map the area in great detail. Assisting King in leading the exploration under the direction of the War Department was Major General A. A. Humphreys. Members of the expedition included the botanists and staff members William Bailey and Sereno Watson who collected approximately 19,000 plant specimens [at the conclusion of King’s expedition]. Plants were only collected in Nevada and Utah from June 1867 to August 1869. Asa Gray appointed Bailey as botanist of the expedition, who spent nine months collecting plants, but a persistent illness caused him to resign. Sereno Watson, who was previously an unpaid volunteer helping with the topographic studies, replaced Bailey. Assistant geologist Mr. James D. Hague and assistant Arnold Hague also took part in the exploration of this territory. From June 1867 to August 1869, Robert Ridgeway served as the expedition’s zoologist collecting primarily ornithological specimens between Sacramento, California and Salt Lake City, Utah. Mr. King and his assistant, Messrs. S. F. Emmons, made large collections of crystalline rocks along with the help of Prof. Ferdinand Zirkel. Smithsonian paleontologist Fielding B. Meek was also part of the exploration’s team, and was assisted by James Hall and R. P. Whitfield.


  • Bartlett, Richard A. Great Surveys of the American West. Norman, Oklahoma: University of Oklahoma Press, 1962.
  • Harvard University. “William Whitman Bailey Papers.” Harvard University Herbaria, http://www.huh.harvard.edu/ Libraries/archives/BAILEYWW.html
  • Watson, S. United States Geological Exploration of the Fortieth Parallel. Volume 5 Botany. Washington D.C.: Government Printing Office, 1871.
  • Goetzmann, W. H. Exploration and Empire. New York: W.W. Norton and Company, 1966.
  • Moore, J.G. King of the 40th Parallel. Stanford, Calif: Stanford General Books, 2006.
  • Harvard University. “Sereno Watson Papers.” Library of the Gray Herbarium, http://www.huh.harvard.edu/ libraries/archives/WATSON.html
  • Watson, S. 1871. List of plants collected in Nevada and Utah, 1867-’69: Numbered as Distributed. Washington D.C.: United States Geological Exploration of the 40th parallel, 1871.
  • Wilson, R. The Explorer King. New York: Scribner, 2006.

Date Range

1867 - 1871


  • Animals
  • Geology
  • Birds
  • Plants
  • Paleontology
  • Botany
  • Ornithology


  • United States
  • Colorado
  • California
  • Utah
  • Nevada


Expedition name