The Civil War, from 1861 to 1865, focused on Northern efforts to prohibit slavery in western territories, including the Great Plains. Most battles occurred east of the Mississippi River. Federal officials considered the western theater secondary. They withdrew regular troops from the Great Plains and recruited volunteers, most of whom served in militias, to stay in the West and fight Native Americans. Partisans waged a guerrilla war, especially in eastern Kansas and western Missouri. In the long run, the war intensified federal authority in the Plains, speeding the dispossession of Native Americans, consolidating the reservation system, and escalating the Plains Indian Wars.
In the Southern Plains, the war divided the Five "Civilized" Tribes, who had been removed from the Southeast to Indian Territory during the 1830s. All five signed treaties with the Confederacy but provided troops to both armies and fought an internal civil war. In reprisal, the Union recruited Native "home guards," invaded Indian Territory, and seized one-half of tribal lands to create reservations for Native Americans removed from Kansas. On the western Plains, Colorado militias warred against Cheyennes and Arapahos, massacring 150 at Sand Creek. In the Northern Plains, the United States forced the Sioux out of eastern Dakota Territory after the Santee Sioux Uprising of 1862 in Minnesota. Congressional initiatives, including the Homestead Act, transcontinental railroad land grants, the Land Grant College Act (Morrill Act), and the Department of Agriculture, encouraged rapid agricultural settlement of the Plains. The Civil War intensified westward expansion, dispossession, the reservation system, and the military subjugation of the Plains Indians.
Kenneth J. Winkle University of Nebraska-Lincoln
Josephy, Alvin M. The Civil War in the American West. New York: Random House, 1991.