O'Shea Spencer, 20, stands in front of the remains of a hogan structure. Campers set structures on fire in preparation for the Army Corp's 2 p.m. deadline to leave the Oceti Sakowin protest camp on February 22, 2017 in Cannon Ball, North Dakota. Activists and protesters have occupied the Standing Rock Sioux reservation for months in opposition to the completion of the Dakota Access Pipeline. #

One day before a government order to leave the area, the United States Army Corps of Engineers announced that a permit to build a pipeline under the Missouri River just outside of the Lakota Sioux reservation of Standing Rock, North Dakota, was denied. The self-described "water protectors" celebrated the news on December 4, 2016. #

An American Indian Movement supporter drives through the Oceti Sakowin camp just outside of the Lakota Sioux reservation of Standing Rock, North Dakota, on December 3, 2016. #

Native Americans and other activists celebrate after learning an easement had been denied for the Dakota Access Pipeline at the Oceti Sakowin Camp on December 4, 2016. #

In this Thursday, December 1, 2016 photo, Cat Bigney, part of the Oglala Native American tribe, waits on the shore of the Cannonball river for travelers to arrive by canoe at the Oceti Sakowin Camp where people have gathered to protest the Dakota Access oil pipeline. #

Military veterans huddle together to hold a United States flag against strong winds during a march to a closed bridge outside the Oceti Sakowin Camp on December 5, 2016. #

On the day of a government order to vacate the area, hundreds of United States military veterans vowed to defend the Standing Rock protest camp and march through a winter blizzard to the scene of recent clashes with state police and the national guard just outside of the Lakota Sioux reservation of Standing Rock, North Dakota, on December 5, 2016. #

Martan Mendenhall, an Army veteran and Blackfoot Indian, joined other military veterans in a march to in support of the "water protectors" at the Oceti Sakowin Camp on December 5, 2016. #

Military vehicles are staged near the path of the Dakota Access pipeline Thursday, February 9, 2017 near Cannon Ball, North Dakota. The developer says construction of the Dakota Access pipeline under a North Dakota reservoir has begun and that the full pipeline should be operational within three months. #

In this Wednesday, February 1, 2017, aerial image taken from a video by KXMB in Bismarck, North Dakota, law-enforcement officers line up against protesters during the eviction of about 40 Dakota Access pipeline opponents from a camp on private property owned by the pipeline developer where the protesters set up on higher ground near their flood-prone main camp. Major General Malcolm Frost said the Army was following the steps outlined in President Donald Trump's order earlier this month for a fast review of requests to approve the pipeline. #

In this February 16, 2017, photo, an abandoned teepee is surrounded by melted snow at the Dakota Access oil pipeline protest camp. The camp is on federal land, and authorities told occupants to leave by Wednesday, February 22 in advance of spring flooding. #

A man who did not want to be identified loads a teepee canvas on his vehicle as he leaves the Dakota Access pipeline opponents' main protest camp on February 22, 2017. #

Chanse Zavalla, 26, from California, watches a building burn after it was set alight by protesters preparing to evacuate the main opposition camp near Cannon Ball, North Dakota, on February 22, 2017. #