Historian Fredrick Jackson Turner influenced the concept of American exceptionalism during the late 1800s. According to the Turner thesis, Americans refined the concept of democracy on the frontier, and Indigenous peoples were obstacles to progress. Even sympathetic settlers saw these cultures as primitive and dangerous. This spurned efforts to assimilate Native peoples into American culture.

The Indian Civilization Act of 1819 funded missionary schools, and in the 1870s Congress provided $100,000 for boarding schools to assimilate Indigenous peoples into American society. Sites like the Carlisle Indian Industrial School, often far from reservations, employed practices from POW camps. Schools for juvenile delinquents made Indigenous children adopt European names and dress while training them for low-income jobs. According to accounts by Sun Elk, a resident at the Carlisle School, the curriculum depicted Indigenous people as violent and backwards. Some parents sent their children due to the squalid conditions at the reservations, and agents took other children by force. Beatings and sexual assault by instructors contributed to lifelong issues like post-traumatic stress disorder.

US expansion continued beyond the Pacific coast. The Kanaka Maoli of Hawai’i recognized the threat of European powers and formed a written language, established democratic institutions, and earned recognition as an independent nation.