Why did the U.S take land from the Native Americans on the Great Plains?

The U.S. took land from Native Americans on the Great Plains primarily due to westward expansion and the belief in Manifest Destiny, which held that Americans were destined to expand across the continent. This expansion was driven by economic interests, including the desire for agricultural land and resources, as well as the discovery of gold and other minerals. The government often employed treaties that were frequently broken, along with military force, to displace Native tribes from their ancestral lands, leading to significant loss of life and cultural disruption.