1750s - Sioux arrive at Black Hills

      The first bands of Sioux drift out of the northern woods of Minnesota, pushed west by better armed enemy tribes such as the Chippewa and Cree.  European traders had met them on the upper Mississippi a century earlier, but now, as they migrated south and west, they broke into three main divisions: the Teton, the Middle, and the Eastern Sioux.

  After moving out of the woodlands of Minnesota, the Sioux became the lords of the Great Plains when they acquired horses in the middle 18th century.  The Black Hills became their sacred homeground, a territory they would win in treaty, and loose when the federal government refused to protect Sioux lands from settlers and gold miners in the 1870s.

http://www.hanksville.org/daniel/lakota/BlackHills.html

        Obtaining guns and horses enabled the Tetons to thrive as nomads on the Great Plains and shaped them into a migratory culture that moved with the buffalo, their 'grocery store on the hoof.'  Soon, they became one of the most prosperous native groups in America at the same time European colonists were fighting for independence from the King George III of England.

http://www.spartacus.schoolnet.co.uk/PRgeorgeIII.htm