The discovery of what resource, in 1874, in the Black Hills of South Dakota caused the U. S. government to break their treaty with the Dakota Sioux

Gold.

Explanation:

A series of clashes between the Northern Cheyenne, Lakota Sioux and the United States that took place in the years between 1876 and 1877 for the occupation of the Black Hills was known as the Great Sioux War. The discovery of the gold in the Black Hills and the U.S government's desire to establish its control over the Black Hills were the main causes of the war.

there were 6 major base camps.   the base camps were located in alva, fort reno, fort sill, the madill provisional internment camp headquarters, mcalester and camp gruber.