Final answer:
The American frontier in 1860 stretched from the eastern Great Plains to the West Coast and was inhabited by numerous Native American tribes. Legislation and westward migration pushed by settlers often led to the displacement of these tribes and renegotiation of earlier treaties. The notion of the frontier played a significant role in shaping American character, as argued by Frederick Jackson Turner's Frontier Thesis.
Step-by-step explanation:
In 1860, the American frontier was characterized by the western edge of settlement by European Americans, which at that time stretched from the eastern Great Plains to the West Coast. The region was home to diverse Native American tribes such as the Sioux, Cheyenne, Comanche, and others, who had been living on these lands for centuries. After the Louisiana Purchase and subsequent explorations, many settlers were moving westward, influenced by events like the California Gold Rush and the completion of the Transcontinental Railroad. The frontier was also directly impacted by legislation such as the Homestead Act of 1862, which encouraged westward migration by offering land claims. These actions often involved displacing Native American tribes and renegotiating treaties that had guaranteed them land.
By the 1880s, the frontier began to close due to increased settlement. Conflicts and the forced removal of Native Americans, such as through the Indian Removal Act, pushed tribes off their ancestral lands and into reservations. The idea of a Permanent Indian Frontier faded as settlers encroached on these areas, leading to clashes and the breakdown of the possibility for a Pan-Indian identity.
Historian Frederick Jackson Turner's Frontier Thesis posited that the American frontier played a critical role in shaping the American character and democracy. However, by 1890 the U.S. Census Bureau declared the frontier closed, raising questions about the future of American expansion and the fate of Native American tribes who had been forced to cede their lands.