Lewis and Clark's 1804-1806 expedition crossed the pathway that runs through Montana as part of a grand adventure 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 changed life in this land forever. In the 19th century, North America was in turmoil as Indian nations recovered from five waves of smallpox and pushed west while Europeans raced to conquer more territory. Although others had explored, traded, and trapped in the Northern Plains, Lewis and Clark were the first to come for military, scientific, and economic development reasons, and their expedition shaped agendas and relationships between cultures and between people and the land that remained unresolved in the West. The Corps of Discovery included Indians, French, Euro-Americans, men of mixed European and Indian descent, one black person, a woman, and a baby, and Indian people of many nations fed, guided, and helped the expedition 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 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 whose diversity is part of the region's identity, and it still contains places where the landscape, wildlife, and native plants appear much as the Corps recorded them, alongside lasting evidence of cultural cooperation, conflict, and collisions in values that have defined the West for two centuries.