The struggle for Native American rights continues.

That's the message of an 11-foot mile-marker post from the Standing Rock Sioux Reservation in North Dakota, a recent addition to the National Museum of the American Indian's groundbreaking exhibition "Nation to Nation: Treaties Between the United States and American Indian Nations."

The mile marker was made by activists gathered at the Oceti Sakowin (Great Sioux Nation) camp to protest the Dakota Access Pipeline. The mile marker features hundreds of handmade signs pointing to the reservations, cities, states and countries represented by some of the 12,000 protesters who tried to block the pipeline's construction under the Missouri River just north of the reservation.

At the core of the protest was the sovereignty of the Standing Rock Sioux Tribe, which is why museum director Kevin Gover said the artifact was a poignant conclusion for the exhibition. Its final section, "The Future of Treaties," drives home the fact that these formal documents still influence the lives of Native Americans.

"This isn't just something from the past," Gover said. "Any place west of the Mississippi, the land is tied to a treaty with an Indian nation and the federal government. We want people to get that, that we are all involved in this, we have all inherited it."

Joined by protesters from around the world, the Sioux argued that the pipeline violated a treaty signed more than a century ago that guaranteed them "absolute and undisturbed" use and occupation of the reservation. They say they were not appropriately consulted about the project, which they say threatens their land.

"Standing Rock is familiar to more people, and it illustrates how the tribes feel about the treaties and the importance they have in native life," Gover said. "There's always been environmental insults, taking of resources, but this was a tipping point."

Hickory Edwards, a member of the Onondaga Nation who was at the camp, donated the mile marker. He contacted Gover to ask whether the museum wanted the artifact after protesters were evicted earlier this year. He drove it 1,600 miles to the museum's collections lab, and it was installed in October.

"We obviously have a special connection to Indian country," Gover said. "We are well trusted, they rely on us to represent them well."

Since opening in 2014, "Nation to Nation" has showcased several treaties signed by U.S. officials and leaders of Indian nations. The exhibition will continue to introduce new ones every few months. Museum officials have worked with the National Archives to display the fragile, priceless documents, which can be displayed only for a few months.

The continued unveiling of treaties emphasizes their influence and importance, Gover said.

"We really want the treaties to be seen, as with the Declaration of Independence and the Constitution, as part of the foundation of the United States," he said.

Author information: Peggy McGlone joined the Washington Post in 2014 as its local arts reporter. Prior to that, she covered the arts for The Star-Ledger in New Jersey for more than a decade.