Coming from a modest family background, Smith traveled to St. Louis and joined William H. Ashley and Andrew Henry's fur trading company in 1822. Smith led the first documented exploration from the Salt Lake frontier to the Colorado River. From there, Smith's party became the first United States citizens to cross the Mojave Desert into what is now the state of California but which at that time was part of Mexico. On the return journey, Smith and his companions were likewise the first U.S. citizens to explore and cross the Sierra Nevada and the treacherous Great Basin Desert. In the following year, Smith and his companions were the first U. S. explorers to travel north from California (on land) to reach the Oregon Country. Surviving three Native American massacres and one bear mauling, Jedediah Smith's explorations and documented travels were important resources to later American westward expansion.