John Charles Fremont popularly known as The Pathfinder during his times–played a major role in opening up the American West to settlement by pioneers. His reliable accounts, including published maps, narrations, and scientific documentations of his expeditions, guided emigrants overland into the West starting in the mid-1840s. Fremont was born illegitimate to a Quebecois father and a Virginian mother. Through the lucky circumstance of obtaining highly influential patrons at his parents’ adopted home city of Charleston, South Carolina, he was appointed second lieutenant in the United States Topographical Corps and quickly rose within its ranks. Through the influence of his father-in-law, Senator Thomas Hart Benton of Missouri–the powerful chairman of the Senate Committee on Military Affairs–he led his first expedition to the Rocky Mountains in 1842. His second expedition–the subject of this book– succeeded in charting all of the way to California, mapping and confirming the Oregon Trail as the route for pioneers heading toward the West.