As seen from the air, the land is an expansive, grayish-brown terrain cracked open by the winding Missouri River with scattered clusters of black dots. On the ground, the dots become cows — so many cows — and the land becomes a roiling sea of prairie grass heaving under currents of wind you can see coming and going from miles in every direction. The reservation covers some 4,200 square miles in north-central South Dakota; it is the fourth-largest Indigenous reservation in the continental United States. Officially, it is home to some 8,000 people, though census figures systemically undercount Indigenous communities...