Frémont's most important work, chronicling his seminal expeditions that revealed the paths and trails that were to be the highways by which the gold seekers would rush to California beginning in 1849. The first portion of the work reprints Frémont's report of 1843, covering his 1842 expedition to the Rocky Mountains, the second portion records his expedition of 1843-1844, delineating the major sections of the route subsequently followed by thousands of Oregon immigrants. This Senate issue contains scientific data not present in the smaller House issue. Cowan p.223-4; Graff 1436; Howes F370; Wagner-Camp 115:1; Zamorano Eighty #39.