While the Wilkes expedition was returning to New York, a surveyor named John C. Fremont was planning an expedition of his own. That summer, Fremont met a man named Kit Carson on a Missouri riverboat. Carson, an experienced frontiersman, led Fremont down along the Front Range of the Rockies in 1842. This map is a product of their trip.
At that time, the only EuroAmerican settlements north of Spanish lands were Fort Laramie, Fort St. Vrain, and Bent's fort. EuroAmericans present at the time were primarily engaged in fur trapping and trading with the natives. The fur trade, which sent beaver pelts back east to make fashionable hats, almost wiped out the beaver and had a significant impact on Colorado's rivers.