American pioneers may have thought they were moving into a wilderness, but the West was home to large numbers of American Indians. Before pioneers and entrepreneurs could go west to pursue their economic dreams, the U.S. government would have to remove this obstacle to American expansion. Through treaties—most of which Americans broke—and war, white Americans conquered the Indian tribes inhabiting the Great Plains during the nineteenth century. After the native population was largely subdued, those who wanted to reform Indian policy focused on carving up tribal lands and forcing Indians to assimilate into American society.