Jefferson had long hoped to send an expedition west of the Mississippi River, the interior of which which was largely unknown to Americans. The Lewis and Clark expedition had several goals. The first, Jefferson said, was to pave the way for expansion of the furt trade into the region. Another was to forge relationships with the peoples that lived in the area, most of which Americans knew only by their reputation among other Indian people. Jefferson also instructed the expedition to attempt to find a water passage to the Pacific, the fabled Northwest Passage, which had eluded explorers for hundreds of years (because it didn't exist.) As the United States concluded the Louisiana Purchase in 1803, the mission remained the same, except that it changed the tone of diplomatic relations with the Indians that the expedition encountered. The Americans were forging diplomatic relations with people that lived on lands now claimed by the US government. It was also hoped that by exploring the region between the Rocky Mountains and the Pacific Ocean, that the United States might solidify its claim to the area, disputed by several countries.