The US Army Corps of Engineers, which manages the federal land where the main camp protesting the Dakota Access pipeline is located, said it would close public access to the area north of the Cannonball River, including to protesters.
The Corps says in a statement Sunday that it "is seeking a peaceful and orderly transition to a safer location".
Henderson's letter said the Corps has set up a free speech zone on land south of the river.
Neil Young recently celebrated his 71st birthday by traveling to Standing Rock to perform for the individuals gathered at the site protesting against the Dakota Access Pipeline.
Standing Rock Sioux tribal leader Dave Archambault did not immediately return telephone calls on Monday.
Standing Rock tribal members believe the land in which the encampment is on is owned by the Sioux through a more than century-old treaty with the US government.
It's the federal government's job to peacefully close the camp because it allowed people to stay there in the first place, Gov. Jack Dalrymple said in a statement Saturday.
Last week, police shot powerful water cannons and rubber bullets to drive protesters from a bridge near the site, including members of the Standing Rock Sioux tribe who claim the building of the pipeline will affect their water resources and sacred grounds. Pipeline developer Energy Transfer Partners disputes that and says the 1,200-mile pipeline through the Dakotas, Iowa and IL will be safe. "Standing without weapons and praying, the water protectors endure human rights abuses in sub freezing temperatures", Young writes.
With winter looming, the Corps has made a decision to close the land north of the Cannonball River where the Oceti Sakowin protest encampment have flourished on December 5, also citing the confrontations between protesters and authorities, according to a letter Archambault said he received.
3 dead, 5 sick from church Thanksgiving dinner
About 835 people attended the Thanksgiving meal on Thursday in the suburb about 45 miles northeast of San Francisco . The questionable meal was prepared by Golden Hills Community Church at Antioch's American Legion Hall.
The action against the pipeline has ignited local and global solidarity and attracted more than 300 Native American tribes from across the U.S.in a show of unity that is being called historic.
As of Monday afternoon, the group had raised more than $495,000 that Diggs said will go toward establishing services at the protest camps, such as medical and supply tents, secure lines of communication and heating systems to help protestors through the winter.
The Corps' letter came after residents in the area expressed feeling unsafe and frustrated with how the protest has swelled to scores of self-described "water protectors".
"If you believe in the inalienable rights of people; the right to clean drinking water, the right to food & shelter and the right to freedom then you have to support standing rock. This is where our people have been for thousands of years".
North Dakota's notoriously brutal winters may help empty the camp of protesters, many of them who are from out of state, Kirchmeier said.
However, the Corps says it won't forcibly remove people from a massive camp used by those opposed to the Dakota Access pipeline, though it's still unclear how the eviction notice will be enforced.
He did consider rerouting the pipeline away from tribal land and the river they are protecting, but Energy Transfer Partners CEO Kelcy Warren, told Associated Press that they won't even consider that possibility.
The Obama administration in September postponed final approval of an Army Corps permit required to allow tunneling beneath the lake, a move meant to give federal officials more time to consult tribal leaders. Protests were mostly peaceful until they turned violent in late November.