Part of the 1803 Louisiana Purchase by the United States, Missouri earned the nickname "Gateway to the West" because it served as a significant departure point for expeditions and settlers heading to the West during the 19th century. St. Charles, just west of St. Louis, was the starting point and the return destination of the Lewis and Clark Expedition, which ascended the Missouri River in 1804, to explore the western lands to the Pacific Ocean. St. Louis was a major supply point for decades, for parties of settlers heading west.