This camp is where thousands of people, indigenous and otherwise, have gathered, bound by a unified purpose.
Just hours later, the corporation behind the pipeline, Energy Transfer Partners, said it would fight to continue its work as planned.
These are a few of the people who helped the Standing Rock Sioux get to this point -- and why they'll keep the fight going.
Blaze Starkey, a Lakota educator from the adjacent Standing Rock Sioux Reservation, sees the Army's decision as "a great step toward victory." But he hopes issues that came to light in recent months don't go overlooked.
"It doesn't address the police violence and militarization. It doesn't address the racism that we live with every day and that I think has been exposed to the world," he says. "It doesn't address treaty issues that have been raised and it doesn't address similar circumstances that are faced by tribes all over the United States."
Starkey runs a school in the camp that has served up to 45 kids. They were constructing new buildings for the school -- called Mni Wichoni Nakicizin Owayawa, or The Defenders of the Water School -- as recently as this weekend.
He says the school is an attempt to do what the educational system has failed to do on its own: provide native children access to their language, culture and who they are. Even Standing Rock High School only has a handful of native teachers.
"As much as possible, we want to give a traditional Lakota education," Starkey says. "But we also want them to be superstars in reading, science, math and writing -- not just so they can excel in the system but so they can critically address the system."
In Starkey's mind, the school's possibilities go beyond the status of the camp or the pipeline. He hopes it will remain and flourish -- on this land or elsewhere -- as a long-term option for his community.
Luna Meng first began following the movement on Facebook two months ago from her home in Port Townsend, Washington.
The 50-year-old mother who homeschools her three kids, made her obsession a lesson plan.
"That's how I teach my children," she says.
But at a certain point, she couldn't sit on the sidelines. So Luna left her children with a friend, writing them a long letter in case she didn't make it back.
"I do this for you," she wrote. "I do this for the next seven generations."
She and her husband Misha, 50, rolled into the camp on Thanksgiving Day with a caravan of about 45 people from their hometown.
The group brought with them a 21-foot portable kitchen, 200 pounds of fresh salmon caught by local fishermen, 400 pounds of grains and 500 pounds of organic vegetables donated from their local farmer's market. They also brought $10,000 they had raised.
It's this sort of generosity that's helped define the camp, where donations of clothing, winter gear, toiletries and more pile high and people look out for one another.
The Mengs are living in their converted 1972 Portland transit bus, which can sleep 10 people. A wood-stove pipe runs out the side, and curls toward the sun. It's an explosion of quilts, bedding and sweaters inside. Behind the driver's seat is an altar of crystals.
Before the Army Corps decision on Sunday, the couple was planning on moving their children to the camp, because what's evolved here is something historic.
"It's the first time we white people are coming together with all these First Nations folks to live in a village and in harmony," Misha says. "It's an incredible learning opportunity."
Vanessa Red Bull, 53, of Virginia came to this camp in September to serve as a medic.
"It's not just for us. It's for humankind," says Red Bull, who is Cherokee Nation. "We have a responsibility."
She's helped people with common colds, anaphylactic shock, broken bones, burns and cuts. And as one of the medics who goes out to the Backwater Bridge during "actions" -- when water protectors walk out to one side of the bridge to stand in opposition to police on the other side -- she's seen far worse.
When tensions erupted a couple weeks ago, she ran from one person experiencing a grand mal seizure to someone else having a cardiac episode that required CPR.
Back at the camp, she's helped people with lingering respiratory problems from mace and tear gas. She points toward the decontamination area for those who've been sprayed. Nearby are spaces reserved for emotional wellbeing. There's a midwifery tent, one for herbal treatments, another for Western medicine. There's also a place for those seeking a massage therapist, acupuncturist or chiropractor.
A bus from Portland, Oregon, has been transformed into an infirmary. And then there's the donated RV that came with an EKG machine.
"Being native, we're used to promises being made and not fulfilled," Red Bull says. "But look around. I see hope for humanity."
Ramsi Tora, who does outdoor education for inner-city youth, came to the camp a few weeks ago from Harlem in New York City.
Tora, who has been involved with Black Lives Matter, sees a difference in the challenges facing Native Americans. This is part of the reason he traveled here.
"Our struggles are more obvious because we're in big cities," says Tora, 26, who's both African-American and Japanese.
"The indigenous communities have been marginalized in ways that weren't obvious to the rest of the country because they live on these reservations."
Reception in the camp is sporadic at best -- except on top of a single hill that's playfully dubbed Facebook Hill. Mike Cobb, 46, stands beside his contribution to the self-sustaining measures that flourish here.
Cobb, of Portland, Oregon, came here a couple weeks ago with his bike in tow. But this isn't just any bike, though. It's a "Rock the Bike" that generates electricity through pedaling and -- in this configuration -- can charge up to 25 phones at a time.
This is especially important here and now, when citizens can tell the story that, he says, major media misses.
"In this off-the-grid environment, I want to help people do what is difficult, like charge their phones," he says. "I'd like as many authentic angles as possible to be brought into public view."
In the days leading up to the Army Corps decision, the camp was abuzz in preparation for veterans who'd be arriving in droves. More than 2,000 had answered a social media call to stand for Standing Rock. As many as 5,000 vets planned to show up.
Volunteers shoveled snow, making room for large military tents. Additional chaplains arrived to be on hand in case PTSD reared its ugly head. A large registration tent gave the vets a starting point to connect with one another and report for duty, so to speak.
The surge in camp numbers served to defy, even more, the Monday deadline for evacuation that authorities set last week.
"Hopefully the government will understand we're not playing around," said Steve Perry, 66, a Vietnam vet who pulled in Saturday afternoon after a 17-hour drive from Traverse City, Michigan.
Perry, an Odawa-Ojibwe, wore a jacket with a patch that read: Disorderly veteran. Don't bother me. His fingers were adorned with Native American rings, and he wore a beaded Odawa floral pattern hat.
He's no stranger to fighting against pipelines and the threat they pose to water. He tried to shut down the aging Enbridge Line 5 pipelines that run through the Straits of Mackinac in northern Michigan.
"It's not just an Indian thing," he says. "Without water, we die."