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Peacekeeping

The U.S. Army after 1850 established a series of military posts across the frontier, designed to stop warfare among Native tribes or between Natives and settlers. Throughout the 19th century, Army officers typically built their careers in peacekeeper roles moving from fort to fort until retirement. Actual combat experience was uncommon for any one soldier.

The most dramatic conflict was the Sioux war in Minnesota in 1862 when Dakota tribes systematically attacked German farms to drive out the settlers. For several days, Dakota attacks at the Lower Sioux Agency, New Ulm, and Hutchinson killed 300 to 400 white settlers. The state militia fought back and Lincoln sent in federal troops. The ensuing battles at Fort Ridgely, Birch Coulee, Fort Abercrombie, and Wood Lake punctuated a six-week war, which ended in an American victory. The federal government tried 425 Natives for murder, and 303 were convicted and sentenced to death. Lincoln pardoned the majority, but 38 leaders were hanged.

The decreased presence of Union troops in the West left behind untrained militias; hostile tribes used the opportunity to attack settlers. The militia struck back hard, most notably by attacking the winter quarters of the Cheyenne and Arapaho tribes, filled with women and children, at the Sand Creek massacre in eastern Colorado in late 1864.

Kit Carson and the U.S. Army in 1864 trapped the entire Navajo tribe in New Mexico, where they had been raiding settlers and put them on a reservation. Within the Indian Territory, now Oklahoma, conflicts arose among the Five Civilized Tribes, most of which sided with the South being slaveholders themselves.

In 1862, Congress enacted two major laws to facilitate settlement of the West: the Homestead Act and the Pacific Railroad Act. The result by 1890 was millions of new farms in the Plains states, many operated by new immigrants from Germany and Scandinavia.