Across Montana lies the pathway of Lewis and Clark, whose 1804-1806 expedition set out to investigate the people and resources of the newly acquired Louisiana Purchase and seek a navigable passage across the Rocky Mountains to the Pacific. Like earlier French and Spanish voyages across North America, the Corps of Discovery returned with information that would change life in this land forever. In a 19th century North America marked by upheaval, with Indian nations recovering from five waves of smallpox and pushing west as Europeans raced to conquer more territories, Lewis and Clark were the first to come to the Northern Plains for military, scientific, and economic development reasons. Their expedition shaped agendas and relationships that people of the West are still working out between different cultures and between people and the land. The Corps of Discovery included Indians, French, Euro-Americans, men of mixed European and Indian decent, one black, a woman, and a baby, and Indian people of many nations fed, guided, and helped the Corps with few violent altercations. In what is now Montana, the expedition explored 1,900 miles of wilderness, catalogued 63 species of plants and animals new to science, and charted significant geographic features, including seven places now recognized as National Historic Landmarks and Monuments: Pompeys Pillar, the Great Falls Portage, the Three Forks of the Missouri, Lemhi Pass, Lolo Pass, Traveller's Rest, and the Upper Missouri Breaks. Montana remains a land of many cultures where landscapes, wildlife, and native plants can still appear much as the Corps recorded them in their journals, alongside enduring evidence of cultural cooperation, conflict, and collisions in values that have defined the West for two centuries.