Yes its true that Native Americans are the largest minority in both North and South Dakota.
They represent about 4 percent in North Dakota and 7 percent in South Dakota, making them the largest minority group in each state.
In the late 19th century, white settlement intensified in South Dakota after a gold rush in the Black Hills which triggered a number of Indian War.
South Dakota is still largely rural and has the fifth lowest population density among U.S. states.