As was the case with many white trappers, Carson became somewhat integrated into the Indian world; he travelled and lived extensively among Indians, and his first two wives were Arapahoe and Cheyenne women. Carson was evidently unusual among trappers, however, for his self-restraint and temperate lifestyle. "Clean as a hound's tooth," according to one acquaintance, and a man whose "word was as sure as the sun comin' up," he was noted for an unassuming manner and implacable courage.

In 1842, while returning to Missouri to visit his family, Carson happened to meet John C. Fremont, who soon hired him as a guide. Over the next several years, Carson helped guide Fremont to Oregon and California, and through much of the Central Rocky Mountains and the Great Basin. His service with Fremont, celebrated in Fremont's widely-read reports of his expeditions, quickly made Kit Carson a national hero, presented in popular fiction as a rugged mountain man capable of superhuman feats.