6 copies of ¡Hacia el Oeste! Lewis and Clark opened the doors for westward expansion when they set out in 1804 to discover what lay beyond the Mississippi. By the middle of the century, mass migration to the west had begun. In the 1880s, many people moved west to seek their fortunes. Find out what happened along the way, and learn about other industries that were born as a result of westward expansion and the Gold Rush.