The reason the US government wanted to contain Native American tribes on reservations was B. the government wanted to free up land for American settlers out West
As European settlers expanded westward in the 19th century, they sought access to fertile land for agriculture, mining, and other economic pursuits.
Native American tribes occupied vast areas of land in the West, and the government aimed to relocate them to designated reservations to make way for non-Native settlement and economic development. This policy was often driven by the belief in Manifest Destiny, the idea that it was the destiny of the United States to expand across the continent.