The Exploring expeditions of James C. Fremont:
1842 - Fremont's first western expedition resulted in mapping the Oregon Trail as far as South Pass to help encourage emigration.
1843-1844 - His second expedition followed a southern route along the Kansas and Republican rivers before joining the Oregon Trail near the Sweetwater River and exploring from South Pass to Fort Vancouver. Although expected to return along the Oregon Trail, Fremont detoured via California.
1846 - This third expedition focused on the central Rockies (source of the Arkansas, Rio Grande, and Colorado rivers), exploration of the Great Salt Lake and surrounding territory, and surveying possible passes in the Sierra Nevada mountains of California.
1848 - Funded privately by St. Louis investors, Fremont's fourth expedition planned to cross the Sierra Nevada again in winter after following the 37th parallel through the San Juan mountains. Trapped there in the snow, the expedition was considered "a disaster" after survivors arrived in Taos, New Mexico.
1853-1854 - In a fifth expedition, Fremont attempted a midwinter crossing of the San Juan Mountains by following a more northerly route to the Great Basin. Seeking a route suitable in winter for the transcontinental railroad, this privately-financed company also endured disaster, but finally reached southern Utah.