Captain Benjamin Bonneville's map of Northern California, Northern Nevada, Utah and the Northwest region west of the Rocky Mountains is perhaps the single most important map of the region published in the 1830s.
Captain Bonneville's map of the region west of the Rocky Mountains is one of the most important and accurate maps of the region between the explorations of Lewis & Clark and John Fremont, and represented a significant leap forward in the depiction of the region. Rather than simply building on the mapping of the region by earlier mapmakers, such as Arrowsmith & Tanner, Bonneville's map completely redraws the hydrographical template of the region.
Lieutenant Warren's 1859 Memoir spends several pages discussing Bonneville's maps, noting that the maps are "the first to correctly represent the hydrography of the region west of the Rocky Mountains. Although the geographical positions are not accurate, yet the existence of the great interior basins, without outlets to the ocean, of Mary's or Ogden's river (later named Humboldt by Captain John Fremont), of the Mud lakes, and of Sevier river and lake was determined by Captain Bonneville's maps, and they proved the non-existence of the Rio Buenaventura and other hypothetical rivers. They reduced the Willamuth or Multnomah (Willamette) river to its proper length, and fixed approximately its source, and determined the general extent and direction of the Sacramento and San Joaquin rivers. The map of he sources of the Yellowstone is still the best one of that region." (pp. 33-34; excerpted in Wheat, p. 159).
Benjamin Louis Eulalie de Bonneville (1796 - 1878) was a French-born officer in the United States Army, fur trapper, and explorer in the American West. He is noted for his expeditions to the Oregon Country and the Great Basin, and in particular for blazing portions of the Oregon Trail.
Bonneville's career in the West began when at the Jefferson Barracks in 1828. While in Missouri, Bonneville was inspired to join in the exploration of the American West. Bonneville petitioned General Alexander Macomb for a leave of absence from the military, arguing in his request that he would be able to perform valuable reconnaissance among the Native Americans in the Oregon Country, which at the time was under the joint occupation of the U.S. and Britain and largely controlled by the Hudson's Bay Company.
Bonneville's 3 year expedition began in May 1832, when he left Missouri with 110 men, including Nathaniel Jarvis Wyeth. The exploration was funded by John Jacob Astor. The expedition proceeded up to the Platte River and across present-day Wyoming, reaching the Green River in August, where Fort Bonneville was constructed. In the spring of 1833, Bonneville explored along the Snake River in Idaho. He sent a group led by Joseph Walker to explore the Great Salt Lake and locate an overland route to California. Walker discovered a route along the Humboldt River Nevada, as well as Walker Pass across the Sierra Nevada. This second route later became known as the California Trail, the primary route during the California Gold Rush. Some historians speculate that Bonneville sent Walker to California in anticipation of an eventual invasion of Mexican controlled California.
In the summer of 1833, Bonneville traveled to the Wind River Range in Wyoming to trade with the Shoshone. He wrote Macomb summarizing his findings and requesting more time to survey the Columbia and parts of the Southwest before his return. After spending the early winter at Fort Bonneville, Bonneville traveled westward in January 1834 toward the Willamette Valley. He and his men traveled up the Snake River, through Hells Canyon, and into the Wallowa Mountains. In March 1834 they reached Fort Nez Perces, the outpost of the Hudson's Bay Company at the confluence of the Walla Walla River with the Columbia. In July Bonneville made a second trip west, following an easier route across the Blue Mountains, where he met Nathaniel Wyeth along the Grande Ronde River, then on to Fort Nez Perces, and down the Columbia to Fort Vancouver, before returning turning back east. Bonneville spent the winter of 1834-1835 with the Shoshone along the upper Bear River and in April 1835 began the voyage back to Missouri.
After completing the expedition, Bonneville returned to Washington, D.C., via New York City where he met up with his patron John Jacob Astor. While staying with Astor, Bonneville met Washington Irving. Later, Irving visited Bonneville in Washington D.C., where Irving agreed that for the sum of $1000, Bonneville would turn over his maps and notes so that Irving could use them as the basis for his third "Western" book. The result was The Adventures of Captain Bonneville, published in 1837.