Towards the beginning of the nineteenth century, existential Enlightenment ideas on indigenous nations were exchanged for a more biological understanding of human evolution. Furthermore, technological advancements and urban development of the nineteenth century oversaw the end of the Noble Savage – the idea that humans were corrupted by civilization – and replaced it instead with a more aggressive stance on what they saw as primitive, backward indigenous traditions. Thus, one form of scientific racism was replaced with another.
When the Louisiana Purchase was made in 1803, there was little knowledge of the indigenous tribes of the region. Thus, when Lewis and Clark embarked on their expedition the next year, they were given specific directions to study the locations and customs of indigenous tribes of the Northwest. They brought with them biased views of the indigenous tribes they met along the way, and their accounts became instrumental in the development of the American image of the Native Indian as the Noble Savage.