Credit Kristina Barker for The New York Times
CANNON BALL, N.D. — Ranchers are arming themselves before they climb onto tractors or see to their livestock. Surveillance helicopters buzz low through the prairie skies. Native Americans fighting to prevent an oil pipeline near the Standing Rock Sioux Reservation are handing out thick blankets and coats and are building maple-pole shelters that can withstand North Dakota’s bitter winter.
As the first deep freeze looms, many here are bracing for a long fight as the company behind the Dakota Access pipeline races to finish the $3.7 billion project by January, and thousands of protesters tucked into tents, tepees and trailers in prairie camps vow to stop it.
“This is where we are, and where we’re staying,” Retha Henderson said, surveying a bustling camp on the edge of the Cannonball River. “We’re not giving up.”
Ms. Henderson said she had been drawn to the site by memories of her grandfather, an Oglala Lakota, and by dreams. She left her apartment and her catering job in Myrtle Beach, S.C.; gave away her cat; and hitchhiked to the Sacred Stone Camp.
A man stopped by and asked if there was a spare toothbrush. There were 4,000.
“This is my home now,” Ms. Henderson said.
It has been a month since the United States government made an unprecedented intervention in this high-plains battle over the environment, energy development and tribal rights by temporarily blocking the 1,170-mile Dakota Access pipeline from crossing under the Missouri River.
Tribal and environmental activists say that the pipeline would threaten water supplies for the Standing Rock Sioux and millions of others downstream, and that its route would destroy tribal burial grounds and sacred cultural lands. The pipeline company, Energy Transfer Partners, says it has followed federal and state rules and claims that the pipeline would be a safer and cleaner way to move crude oil from fields to refineries.
On Sunday, a federal appeals court removed a major obstacle for the company by rejecting the Standing Rock Sioux’s request for an injunction against the pipeline. The tribe has sued in federal court, arguing that it was not properly consulted about how the pipeline’s route could affect ancestral tribal lands. (The company said Tuesday that it would resume that work.)
The appeals court said crews could resume work on private lands, bringing the pipeline closer to the Army Corps of Engineers land straddling the pipeline’s crucial river crossing.
The corps is responsible for deciding whether to grant the pipeline an easement to cross under the river. It has been reviewing its earlier pipeline-related decisions, made under federal environmental laws, and said on Monday that it hoped to reach a conclusion soon.
In a joint statement from the corps and the Interior and Justice Departments, officials again asked the pipeline company to pause construction within 20 miles of Lake Oahe, the dammed section of the Missouri. The agencies and the tribes will meet this week in Phoenix to discuss the need for nationwide reform on how Native Americans are consulted on major infrastructure projects like the pipeline.
“We continue to respect the right to peaceful protest and expect people to obey the law,” the agencies said in the statement.
David Archambault II, the chairman of the Standing Rock Sioux, said that he was disappointed by the legal setback but that the tribe would make a “full-court press” to urge President Obama and federal officials not to let the pipeline cross the river.
“We’re hoping he does the right thing by our people at Standing Rock,” Mr. Archambault said.
Even with the government-ordered halt, the pipeline’s progress never really stopped.
Crews kept digging ditches and draping sections of the light-green 30-inch pipe into ranchers’ fields not covered by the federal order. And protesters kept dogging them, driving to construction sites as far as 80 miles from their camps to try to halt work.
On Monday, a holiday that many celebrate as Indigenous Peoples Day instead of Columbus Day, scores of protesters rallied and pitched a tepee beside a section of pipe near the tiny farming town of St. Anthony. Twenty-seven people were arrested. In all, about 130 have been arrested since the large-scale protests began this summer.
Ranchers are becoming edgy. Sheriff’s deputies worried about being identified at protests have taken off their name tags, and some say they have been followed home. Local officials here are increasingly exasperated because Washington has declined or ignored their requests, they say, for emergency funds and federal law enforcement officers.
“The camp is on federal land, and the federal government has not responded to official requests for resources,” said Cody Shulz, the chairman of the Morton County Commission.
Local officials also criticized Washington’s move to intervene and pause construction, saying it had prolonged demonstrations that have drained money and left law enforcement stretched thin.
“It’s made this whole situation more confusing in the long run,” said Sheriff Kyle Kirchmeier of Morton County, who has led the law enforcement response to weeks of anti-pipeline demonstrations. “It has dragged it on longer and put an uncertainty on the whole thing.”
Jon Moll, 38, a sheriff’s deputy in Morton County, has been working six- and seven-day weeks since the summer. He has carefully pulled down a protester who locked himself to the bucket of an excavator. Deputy Moll described the tensions of a demonstration last month where, sheriff’s officials say, a protester on horseback charged at deputies.
“Some have no problem with us,” Deputy Moll said as he drove past the camps on Saturday, many people offering a quick wave at his sport utility vehicle. “You have people that despise your existence.”
Officers like Deputy Moll say they have been trying to keep tense face-offs in the rolling plains from spiraling into violence. Sheriff Kirchmeier says demonstrators have charged onto private property and attacked pipeline contractors. Demonstrators say security guards for the pipeline unleashed guard dogs on them during a confrontation.
Winter may be coming, but so are new supporters. A group of Comanche teenagers and their parents drove to a camp from Oklahoma over the weekend to march up a rural highway to land that the pipeline would cross. A group of 400 indigenous grandmothers is making plans to come. In South Dakota, people are raising money for 1,000 Oglala Lakota Sioux children to travel to the camps.
“Something bigger than us is happening here,” said LaDonna Brave Bull Allard, a tribal historian for the Standing Rock Sioux who helped found the first camp, on her property, in April.
On Sunday morning, she had just come home from buying breakfast supplies in Bismarck, N.D., for the camp. Her trips these days begin with her husband telling her to be safe.
“We watch every day,” she said. “We have a right to live here.”
A version of this article appears in print on October 11, 2016, on page A10 of the New York edition with the headline: Tension Rising Over Pipeline, Tribes Dig In: ‘We’re Staying’.