BADLANDS NATIONAL PARK, S.D. — Buffalo stroll undisturbed, pausing occasionally to wallow in the grass and caked dirt, while prairie dogs yip intermittently as they dive into their holes and pop out again to survey the landscape. This northern stretch of the park, known as Sage Creek Wilderness, is what the Northern Great Plains used to look like.

Several miles away, in the park’s 133,000-acre South Unit on the Pine Ridge Indian Reservation, the scene is more barren. The U.S. Army forced more than 800 Oglala Sioux families to leave their homes here in 1942 so part of the reservation could be turned into a bombing range. The land has recovered partially, but the bison have yet to return.

That soon could change. The Oglala Sioux and National Park Service are drafting legislation to create the first tribal national park — giving the tribe the right to manage and operate the lands — in an effort to bring buffalo back to the grasslands where they roamed long before human settlement.

These steps would reshape only a portion of the Great Plains, a landscape that has been transformed by corn fields, highways and big-box stores. But for the Oglala Sioux, it is a chance to reclaim an area that was a crucible for the nation’s economic and political expansion in the 1800s.

Ruth Brown, an Oglala Sioux tribal council member who is helping draft the legislation to establish the new park, said: “Our buffalo are going to be coming back to our country.”

The group envisions a herd of more than 1,000 animals to ensure it has sufficient genetic diversity.

Tens of millions of bison used to range freely in North America before they were almost wiped out in the late 1800s. The American Bison Society disbanded in 1935 with the understanding it had saved the species by placing 20,000 animals in conservation herds. There now are an additional 400,000 or so being raised in the United States and Canada for meat production.

But those numbers are not enough for the buffalo to reclaim their traditional role in the ecosystem, especially because even those conservation herds amount to what buffalo herder Duane Lammers calls “islands,” in circumscribed areas. Free-roaming bison provide habitat for grassland birds and other animals by grazing intermittently, leaving the grass at different heights. Cattle ranching, by contrast, leaves the grass at a more uniform level.

The Wildlife Conservation Society relaunched the American Bison Society in 2005, and a coalition of tribes, environmentalists and ranchers have been working to bring them back to areas where there is enough available land.

“We’re in a sort of a renaissance, where conservation groups are realizing it needs to happen on a larger scale,” said Dennis Jorgensen, a biologist and Northern Great Plains program officer for the World Wildlife Fund.

The Badlands — where sediment deposits have been eroded by wind and water over millions of years — is an ideal setting for buffalo to make a comeback. Less suitable for agricultural development than other parts of the Great Plains, the federal Resettlement Administration started buying ranches and farms in 1934 that failed during the Dust Bowl. The government bought more than 10 million acres; nearly 600,000 of them became the Buffalo Gap National Grasslands, west of the Pine Ridge Reservation and the national park.

“It’s just a biologist’s dream, in terms of intact prairie grasslands,” said Trudy Ecoffey, senior wildlife biologist for the Oglala Sioux Parks and Recreation Authority, as she looked out at the dry, largely uninhabited terrain of the park’s South Unit.

In addition, a handful of nonprofit organizations and entrepreneurs are willing to invest in land to put it off-limits to development.

For the Oglala Sioux, who often describe buffalo in more ethereal terms, the effort to gain full control of Badlands’ South Unit and repopulate it with bison has been fraught with tension.

The National Park Service signed a memorandum of agreement in 1976 with the tribe to establish how it would operate the South Unit. Badlands National Park Superintendent Eric Brunnemann said the original plan was “problematic,” because it failed to recognize the fact the Oglala Sioux tribe is “its own country. … This is a government-to-government relationship.”

Even though it makes sense from an ecological and economic perspective, reintroducing buffalo poses a political challenge because some Oglala Sioux own cattle-grazing permits in the area, including on the reservation. On June 11, the tribal council voted to phase out all cattle leases on the South Unit by Oct. 31, 2015.

Although the Park Service issued a record of decision last year outlining how the tribe would take control of the South Unit, obstacles remain. A working group hopes to draft legislation by the end of the year, but it will have to make it through Congress.