Complex sentence: Not recognizing that this was Caddo territory, the United States granted it to the Choctaw Indians in 1832 by the Treaty of Dancing Rabbit Creek, in exchange for the people ceding their land in the American Southeast to the federal government during the period of Indian Removal.
Split into simpler sentences: Not recognizing that this was Caddo territory, the United States granted the lands to the Choctaw Indians in 1832 by the Treaty of Dancing Rabbit Creek. This was in exchange for the Choctaw ceding their land in the American Southeast to the federal government during the period of Indian Removal.