It’s been decades since Madonna Thunder Hawk last saw the valley she grew up in on the Cheyenne River Reservation. It lies buried under the Missouri River. The United States government sent the river rushing over the reservation’s largest town in 1960 as part of a series of post-war federal flood control projects.

In the history of Native American land dispossession in North America, the creation of the Oahe Dam is little more than a footnote. But for Ms. Thunder Hawk, it is her footnote. She couldn’t bear to watch the water consume the land. Then in her early 20s, she says she didn’t fully appreciate that, in various guises, this had been happening to her ancestors for centuries.

The dam wasn’t illegal, or even militaristic – though the U.S. Army Corps of Engineers built it. As with the 370-plus treaties that tribes have negotiated with the government, Ms. Thunder Hawk’s father received some compensation. Like many of those tribes, he didn’t want the money. He wanted to preserve the land.