The most famous of the explorers was John Charles Frémont (1813–1890), an Army officer in the Corps of Topographical Engineers. He displayed a talent for exploration and a genius at self-promotion that gave him the sobriquet of "Pathmarker of the West" and led him to the presidential nomination of the new Republican Party in 1856. He led a series of expeditions in the 1840s which answered many of the outstanding geographic questions about the little-known region. He crossed through the Rocky Mountains by five different routes and mapped parts of Oregon and California. In 1846–1847, he played a role in conquering California. In 1848–1849, Frémont was assigned to locate a central route through the mountains for the proposed transcontinental railroad, but his expedition ended in near-disaster when it became lost and was trapped by heavy snow. His reports mixed narrative of exciting adventure with scientific data and detailed practical information for travelers. It caught the public imagination and inspired many to head west. Goetzman says it was "monumental in its breadth, a classic of exploring literature".