The expedition lasted from 1804 to 1806, during which time Lewis and Clark and their team traveled extensively throughout the northern Rocky Mountains and Pacific Northwest region, making significant contributions to geography, cartography, natural history, and the knowledge of Native American cultures in the Americas. They were the first non-natives to keep written or documented records of many parts of their journey. Upon their return, these records inspired widespread public interest in the previously almost entirely unexplored area that is now the western United States.