A group of the Fort Laramie treaty riders head out in the morning along the local highway on the Cheyenne River Reservation outside of Bridger, South Dakota on April 16, 2018. REUTERS/Stephanie Keith
Stephanie Big-Eagle rides with the other Fort Laramie treaty riders along Bombing Range Rd. on the Pine Ridge reservation near Scenic, South Dakota on April 20, 2018. REUTERS/Stephanie Keith
A small herd of Buffalo graze near the Sage Creek campground in the Badlands National Park outside of Wall, South Dakota on April 19, 2018. Buffalo or Bison are one of the most sacred animals to the Lakota people and formerly their lifestyle depended on them. Prior to European settlement, about 30 million bison inhabited North America. But by the late 19th century, fewer than 1,000 could be found on the continent, with only a handful of wild bison left in the American West. Badlands National Park is among a handful of organizations trying to restore the herd population. REUTERS/Stephanie Keith
Dave Swallow or "Man Who Walks with Pride" an elder and headsman of the Oglala Lakota Nation gathers with others on the Pine Ridge Reservation to discuss treaties and the treaty ride in Pine Ridge, South Dakota on April 22, 2018. REUTERS/Stephanie Keith
Duane Blindman, age 64, Oglala tribe, from Slim Buttes on the Pine Ridge Indian Reservation poses for a photograph in Van Tassel, Wyoming on April 25, 2018. REUTERS/Stephanie Keith
Two riders with the Fort Laramie treaty ride are seen in a field as a storm approaches off of the Bridges to Buttes Byway in Whitney, Nebraska on April 23, 2018. REUTERS/Stephanie Keith
The Fort Laramie treaty riders pass through a small town on their way to Fort Robinson off of the Bridges to Buttes Byway in Crawford, Nebraska on April 23, 2018. REUTERS/Stephanie Keith
The Fort Laramie treaty riders circle up after their day of riding in Harrison, Nebraska on April 24, 2018. REUTERS/Stephanie Keith
Tatanka Itancan Lone Eagle, age 15, from Bridger on the Cheyenne River Reservation, hugs his horse at the end of the day during the Fort Laramie treaty ride in Scenic, South Dakota on April 19, 2018. REUTERS/Stephanie Keith
Two people with the Fort Laramie treaty ride put up a tipi for an overnight stop in Fort Robinson outside of Crawford, Nebraska on April 23, 2018. REUTERS/Stephanie Keith
Seth Eastman from the Sisseton-Wahpeton Sioux Tribe sleeps in the back of a truck in the "tribal area" on the grounds of the Fort Laramie National Historic Site in Fort Laramie, Wyoming on April 29, 2018. REUTERS/Stephanie Keith
A Fort Laramie treaty rider, Austin Warrior, age 11, and his sister Delores Warrior, 19 months, both from Pine Ridge Reservation are covered with burning sage smoke in Harrison, Nebraska on April 24, 2018.
Chairman of the Cheyenne River Reservation, Harold Frazier (center) wears his traditional head dress prior to arriving in Fort Laramie later that day near Fort Laramie, Wyoming on April 27, 2018. REUTERS/Stephanie Keith
One of the Fort Laramie treaty riders looks over at the actual treaty signing area represented by the three tipis while on the banks of a creek in the "tribal area" on the grounds of the Fort Laramie National Historic Site in Fort Laramie, Wyoming on April 29, 2018. REUTERS/Stephanie Keith
One of Arvol Lookinghorse's horses, ridden by the Fort Laramie treaty riders, is put in a horse trailer for transport back to Green Grass, South Dakota in the "tribal area" on the grounds of the Fort Laramie National Historic Site in Fort Laramie, Wyoming on April 29, 2018. REUTERS/Stephanie Keith
People sit in front of a mural depicting a Buffalo and a traditional looking Native along the main road on the Cheyenne River Reservation in Eagle Butte, South Dakota on May 28, 2018. REUTERS/Stephanie Keith
One of Beatrice Lookinghorse's grand daughters rides a horse around her home on the Cheyenne River Reservation in Green Grass, South Dakota on May 29, 2018. REUTERS/Stephanie Keith
Angel Lookinghorse, sitting with her younger cousins, speaks to her brother, Jayden Lookinghorse riding his horse, on the Cheyenne River Reservation in Green Grass, South Dakota on May 30, 2018. REUTERS/Stephanie Keith
Mahto In The Woods jumps over a small creek while his cousin Jayden Lookinghorse jumps over the creek on his horse on the Cheyenne River Reservation in Green Grass, South Dakota on May 30, 2018. REUTERS/Stephanie Keith
One of Beatrice Lookinghorse's grand daughters plays in the backyard of Beatrice Lookinghorse's trailer on the Cheyenne River Reservation in Green Grass, South Dakota on May 30, 2018. REUTERS/Stephanie Keith