As the harsh North Dakota winter approaches and protests grow even more tense, the Standing Rock Sioux and their supporters are rising to crescendo in the fight against the Dakota Access Pipeline.
Now there's a deadline: Authorities say they must leave the camps by December 5. Demonstrators say they aren't budging.
Here's a look at what they're battling for and how it got to this point.
THE PIPELINE
The Dakota Access Pipeline is a $3.7 billion project that will transport 470,000 barrels of oil a day across four states. Specifically, it will pass through an oil-rich area in North Dakota where there's an estimated 7.4 billion barrels of undiscovered oil. This oil would be shipped to markets and refineries in the Midwest, East Coast and Gulf Coast regions. This way, the project developer says, the United States could tap its own backyard for oil, rather than relying on imports from unstable regions of the world.
The pipeline would also be an economic boon, bringing an estimated $156 million in sales and income taxes to state and local governments as well as add 8,000 to 12,000 construction jobs, the developer says.
But this is the Dakota Access Pipeline on paper. When it comes to the real-world construction, things aren't so clear-cut.
THE STANDING ROCK SIOUX
President Obama talks with Standing Rock Sioux Chairman David Archambault II during the Cannon Ball Flag Day Celebration on June 13, 2014.
The Standing Rock Sioux tribe sued the US Army Corps of Engineers after the pipeline was granted final permits in July. The tribe says the project will not only threaten their environmental and economic well-being, but will also cut through land that is sacred. Construction of it, they say, will "destroy our burial sites, prayer sites and culturally significant artifacts."
Faith Spotted Eagle, who lives on the Yankton Sioux Reservation of South Dakota, says it's not up to researchers to determine what land is sacred.
"Archaeologists come in who are taught from a colonial structure, and they have the audacity to interpret how our people were buried," she says. "How would they even know?"
Ron His Horse Is Thunder, a spokesman for the Standing Rock Sioux Tribe.
She says 38 miles of the Dakota Access Pipeline cuts through territory that still belongs to Native Americans, based on a 1851 treaty signed at Fort Laramie in Wyoming.
THE PROTESTS
For months, hundreds of protesters from around the world have traveled to North Dakota to push back on the construction of this pipeline. The demonstrations have turned violent at times, as police dressed in riot gear tear gassed and pepper sprayed protesters during clashes.
Just before Thanksgiving, on an evening when temperatures dropped below freezing, police sprayed protesters with a water cannon.
THE CAMPS
A few makeshift camps in Cannon Ball, North Dakota, serve as temporary homes for many of the demonstrators. Tipis, tents and food trucks dot the snow-covered ground as flags from other tribes around the nation billow in the sky above.
A Standing Rock Sioux flag flies over a protest encampment near Cannon Ball, North Dakota.
Officials say they are shutting down the camps on December 5. They've also instituted a $1,000 fine for anyone taking supplies to protesters. But as that deadline looms, the people in the camps are digging in their heels, determined to stay.
Snow covers Oceti Sakowin Camp near the Standing Rock Sioux Reservation on November 30, 2016 outside Cannon Ball, North Dakota.
Some residents of Cannon Ball, however, say the camps have been a nuisance. They also say you won't see all Standing Rock Sioux there -- many of the people residing in the shelters are from other parts of the country.
THE ENVIRONMENTAL IMPACT
It's all about who you ask.
Dakota Access claims the pipeline would provide a safer, more environmentally friendly way of moving crude oil, compared to other modes of transportation, such as rail or trucks. Supporters cite the 2013 disaster in Quebec, where a train carrying crude oil destroyed downtown Lac-Megnatic when it derailed.
But one the Standing Rock Sioux's arguments against it is that it doesn't spur the country's move away from crude oil. Americans should instead look for alternative and renewable sources of energy, Standing Rock Sioux Chairman David Archambault II said in September.
Opponents also worry about what the pipeline, which would go under the Missouri River, could do to the water supply if it ruptured.
North Dakota pipeline protests
Fireworks lit the sky at the Oceti Sakowin Camp near Cannon Ball, North Dakota on December 4, 2016, after the Army Corps of Engineers halted the Dakota Access Pipeline route. An executive order by President Donald Trump in January allowed work to resume.
Activists embrace after the December halt of the
Dakota Access Pipeline route. The $3.7 billion project that would cross four states and change the landscape of the US crude oil supply. The Standing Rock Sioux tribe says the pipeline would affect its drinking-water supply and destroy its sacred sites.
An activist rides down from a ridge on the edge of the Standing Rock Sioux Reservation on December 4.
Activists celebrate at Oceti Sakowin Camp on December 4. An executive order by President Donald Trump in January allows work to resume on the Dakota Access Pipeline, which the activists oppose.
Dan Nanamkin of the Colville Nez Perce tribe drums a traditional song by the Cannonball River in Cannon Ball, North Dakota, on Thursday, December 1.
A procession makes its way down to the Cannonball River to take part in a Native American water ceremony on December 1.
Snow covers the camp on Wednesday, November 30.
A person walks through snow and wind on Tuesday, November 29.
People against the construction of the Dakota Access Pipeline speak at a news conference near Cannon Ball on Saturday, November 26.
A sculpture stands at an encampment where protesters of the pipeline have been gathered for months.
People protest along Highway 1806 as they walk past a sprawling encampment on Thursday, November 24.
A man stands along Highway 1806 on November 24.
In this image provided by the Morton County Sheriff's Department, law enforcement and protesters clash near the pipeline site on Sunday, November 20.
Tonya Stands recovers after being pepper-sprayed by police on Wednesday, November 2. Stands was pepper-sprayed after swimming across a creek with other protesters hoping to build a new camp to block construction of the Dakota Access Pipeline.
Dozens of protesters wade in cold creek waters as they confront local police on November 2.
Tribe members make their way back to their camp on Saturday, October 29.
Cousins Jessica and Michelle Decoteau take part in a protest outside the North Dakota state capitol in Bismarck on October 29.
The burned hulks of heavy trucks sit on Highway 1806 on Friday, October 28, near a spot where Dakota Access Pipeline protesters were evicted a day earlier.
Pipeline protesters sit in a prayer circle as a line of law enforcement officers make their way across the camp to relocate the protesters a few miles south on Thursday, October 27. Protesters had camped on private property.
A protester is arrested as law enforcement surrounds the camp on October 27.
Tires burn as armed soldiers and law enforcement officers stand in formation to force Dakota Access Pipeline protesters off the private land in Morton County.
A protester shows where he was hit by a bean-bag round fired by officers trying to force protesters off the private land.
JR American Horse leads a march to the pipeline site on Friday, September 9.
Native Americans head to a rally at the state capitol in Denver on Thursday, September 8. They were showing their support for members of the Standing Rock Sioux tribe in North Dakota opposting the Dakota Access Pipeline.
People hang a sign near what they say was sacred burial ground disturbed by bulldozers in Cannon Ball.
Marlo Langdeau of the Lower Brule Sioux Tribe joins hundreds of Native Americans for a march near Cannon Ball on Sunday, September 4.
Protesters march on September 4 in opposition to the Dakota Access Pipeline.
Native Americans march to the site of a sacred burial ground on September 4.
Native Americans ride with raised fists to the sacred burial ground on September 4 to protest the Dakota Access Pipeline.
The Missouri River is seen beyond an encampment near Cannon Ball, where hundreds of people gathered to join the protest on September 4.
Flags of Native American tribes from across the United States and Canada line the entrance to a protest encampment on Saturday, September 3.
Phil Little Thunder Sr. attends an evening gathering at an encampment of Dakota Access Pipeline protesters on September 3.
Jessica Ravitz contributed to this report from Cannon Ball, North Dakota.