From now until April 4th, 89 American bison calves wait in quarantine. When the fateful day finally arrives, the group will be trucked over the Canadian border and released at a ranch along the Two Medicine River, the area of Montana their ancestors called home 140 years ago.

Related Content The Bison Is Now the Official Mammal of the United States

The genetically pure buffalo, Bison bison, are part of a plan by the Blackfeet tribe to restore the giant bovines to their reservations, bordered by the Lewis and Clark National Forest and Glacier National Park.

Back in 1872, Chris Peterson of Hungry Horse News reported that a Salish and Kootenai Warrior named Running Coyote was having trouble with his tribe. As an apology, he and several friends rounded up buffalo calves on Blackfeet land and brought them over the Continental Divide to the Salish and Kootenai as a gift. The apology didn’t really work out, and ranchers Charles Allard and Michel Pablo took charge of the bison herd, eventually growing it to 300 animals over the next 25 years.

Near the turn of the century, disputes over grazing rights meant the herd had to be sold. Teddy Roosevelt reportedly wanted the animals, but Congress wouldn’t release the funds. So Pablo sold the buffalo to the Canadian government, which shipped the animals to Elk Island National Park, outside Edmonton, Alberta, where the herd has stayed for over 100 years.

Now, according to Matthew Brown from the Associated Press, the bison are being repatriated as part of treaty between U.S. and Canadian tribes signed in 2014. “For thousands of years the Blackfeet lived among the buffalo here. The buffalo sustained our way of life, provided our food, clothing, shelter,” Blackfeet chairman Harry Barnes tells Brown. “It became part of our spiritual being. We want to return the buffalo.”

The tribe hopes that the calves will form the nucleus of a herd that could eventually include 500 to 1,000 free-roaming animals. According to the International Union for Conservation of Nature, which tracks endangered animals, there are currently only 15,000 wild free-range bison in North America out of the half of a million remaining animals. That’s a far cry from the 30 to 60 million buffalo that once roamed the continent and were wiped out by European settlers.

Not everyone is excited, however, about restoring the bovines to the natural landscape. Ranchers fear the buffalo will compete with cattle for grazing land and are afraid the animals will carry brucellosis, a bacterial disease that interferes with cattle reproduction. That’s one reason the National Park Service has culled hundreds of bison in Yellowstone National Park in recent years, to prevent them from leaving the park boundaries and mingling with nearby cattle.

“The difficulty [with Yellowstone bison] is the stigma attached to them. In this case, the animals [coming from Canada] have never been exposed to brucellosis,” Keith Aune with the Wildlife Conservation Society, which is working with the Blackfeet, tells Brown.

For the Blackfeet, the release is more than just an environmental triumph. Having free roaming buffalo in the area means a restoration of part of their traditional culture. “We’re releasing these animals back to the original landscape and back to management of the original people,” Aune tells Peterson. “This hasn’t been done anywhere else in the world.”