Frémont Expedition to Oregon and California (1843 - 1844)

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John Charles Frémont, a lieutenant in the Army Topographical Corps, was commissioned by the U. S. government to explore and map areas of the Pacific Northwest. In his second major land expedition, he set out along the Oregon Trail between Missouri and Fort Vancouver. The trip began from Missouri in June of 1843 and traveled through the prairie lands near the Kansas River. Eventually, the expedition moved from the grassy prairie to a desert-like region, which grew so densely that it often impeded the group’s progress. Frémont then explored portions of the Great Salt Lake in Utah. On November 4, 1843, the expedition arrived at its western limit on the Columbia River. By reaching this point, Frémont had “accomplished the object of uniting [his] survey with [Wilkes’], and thus presenting a connected exploration from the Mississippi to the Pacific.” Although the expedition had been instructed to return eastward through the unexplored Great Basin, poor grass and difficult mountains convinced Frémont to cross the Sierra Nevada Mountains into Sacramento Valley, California, and from there return eastward. Frémont and his men passed through northern Mono County the last week of January of 1844 and reached Long Camp. From there, they traveled to Sutter’s Fort, arriving in March of 1844. The group stayed and rested for a month, and then headed south through the San Joaquin Valley, then easterly along the Old Spanish Trail to pass into Utah. Frémont was not only the leader, but also the botanist on the expedition. He was joined by twenty seven other men including mountain men, trappers, surveyors and cartographers. Among them were botanist John Torrey, surveyor and cartographer Charles Preuss, and famous explorers Kit Carson and Thomas Fitzpatrick. In the last month of travel remaining, all of the botanical specimens collected from California onwards were drenched when the expedition was caught in floodwaters rising from the Kansas River. Some plant specimens survived the hardships of the trip and are now part of the National Herbarium collection.


  • Jackson, Donald and Spence, Mary Lee. The Expeditions of John Charles Frémont. Vol. 1, Travels from 1838 to 1844. Urbana: University of Illinois Press, 1970.
  • Viola, Herman J. and Ralph E. Ehrenberg. Introduction to The Exploring Expedition to the Rocky Mountains, by John C. Frémont, pp. Washington, D. C.: Smithsonian Institution Press, 1988.
  • USDA PLANTS database. United States Department of Agriculture, Natural Resources Conservation Service. National Plant Data Center. (for information on plant species Bouteloua dactyloides, Artemisia tridentate, Sarcobatus vermiculatus, Lasthenia fremontii, Psorothamnus arborescens, and Machaeranthera asteroides).

Date Range

1843 - 1844


  • Plants
  • Botany


  • Oregon
  • San Joaquin Valley
  • United States
  • Sierra Nevada
  • Mono
  • California
  • Great Salt Lake
  • Columbia River


Expedition name