The Last Great Battle of the American West (2009).
Proclamation of 1763, which was the last time that Native sovereignty (in the interior) was considered important to the causes of peace and trade; of course it was only considered, not respected, by Colonial whites (e.g. Washington).
The demand for land by white Americans was enormous, and "The Line" kept moving West after such events as: The Battle of Fallen Timbers (1794) / Louisiana Purchase (1803) /
Indian Removal Act (1830; where white expansion picked up serious momentum) /
Indian Intercourse Act (1834; defined "Indian Territory") / The 1st Wagon Train to Reach the Platte River (1841; it was the origin of the
Oregon Trail) . . . by the early-1840s, Native removal was largely accomplished in the view of white America.
Democratic Review); it provided political, social, economic, and even religious justification for whites to expand West.
The Mexican War (1846 - 1848) finalized most of the U.S. Government's claims in what would become known as the contiguous states (the Gadsden Purchase of 1853 was the last land purchase from Mexico). The Gold Rush in California dramatically increased expansion, and it also proved that "The Line" was no longer an effective solution to the "Native Problem".
An example: A treaty was signed between the Cheyenne & Arapaho Nations and the U.S. Gov't in 1851 where it was agreed that the Cheyenne would relocate to a reservation south of the Arkansas River, giving up all their lands. But, only 6 of the 44 Cheyenne and Arapaho chiefs signed the treaty . . . therefore, most Cheyenne and Arapaho didn't feel that they were bound by the document. Also, "Annuity Payments" on reservations were designed to wean Natives from buffalo, but the system was steeped in corruption, since it was headed by the Bureau of Indian Affairs. Despite all the dishonesty and corruption with the treaties and on the reservations, major warfare had been avoided in the Midwest and the Great Plains.
General John Pope, then in charge of the Missouri Division, vowed revenge; he ordered
General Henry Sibley's troops into action, and they defeated a large number of Santee warriors at Wood Lake. Over 2000 were captured, and 38 were publicly hanged on 26 December, 1862; President Lincoln actually commuted over 300 Native executions. The Lakotas were stripped of their land in SW Minnesota by the Minnesota River, and moved to a reservation on the Missouri River. Sioux resistance (Lakota, Dakota, Nakota, and others) spread westward with the fleeing warriors, and violence on the Great Plains increased.
Enraged Cheyenne, Sioux, and Arapaho warriors raided towns, stage stations, ranches, wagon trains . . . they burned, looted, and killed wherever they could in retaliation for Sand Creek. During the Winter of 1864-1865, these warriors joined kinsmen in the Powder River country, which was the area between the Black Hills and the Bighorn Mountains, which the Lakota claimed as their homeland (although the Lakota had taken it from the Crow Nation a few decades earlier).