The Dakota Access Pipeline (DAPL) is part of the Bakken Pipeline Project (BPP). A 1886 km underground oil pipeline to transport around 470,000 barrels of crude oil a day from North Dakota to Illinois, where it will shipped to refineries. The owner is the Energy Transfer Crude Oil, a Texas-based company and is financed by more than 15 banks around the world.

On November 2016 the project was reported to be around 90% completed and was expected to be delivered by January 2017. However, the section closest to the Standing Rock Sioux reservation (Native American territories) is where the conflict is taking place.

In July 2016, The Standing Rock Sioux Tribe, from North Dakota filed suit against the U.S. Army Corps of Engineers to stop the project. The native tribes argued that the pipeline threatens the Native American cultural sites and their water supply. Furthermore, it does not recognize the “Treaty of Fort Laramie” signed 1868 in which United Stated recognize the Great Sioux Reservation. The motion suit by the native tribes was denied in September 2016. Afterwards they filed an appeal but it was denied again in October the same year.

As a form of protest and to block the ongoing building pipeline, Native Americans founded “spiritual and water protection camps” such as Sacred Stone, Oceti Sakowin camp, Red Warrior, and Rosebud Sicangu. Native have receive support all over the world and protestors in these camps have reach more than 10.000 people.  During protests and blockages, more than 750 people have been arrested, they have faced pepper spray attacks, rubber bullets and sound cannons, among other violent methods  such as attack with dogs which bit at least six people.

At the end of 2016, the Obama US government decided to explore other routes for the Dakota pipeline amid huge protests by Native Americans. As a symbol of solidarity with the native Indians in on December 2016, Veterans took a knee and collectively asked for forgiveness for the genocide and war crimes committed by the United States Military against tribal nations.

However, it seems this decision was short-lived victory as the owner of the project, Energy Transfer Partners, has been a major contributor to the Republican Party and Trump’s campaign. Once Donald Trump became president, he signed an executive order to advance the construction of the pipeline under "terms and conditions to be negotiated”. On February 7, 2017, Trump authorized the Army Corps of Engineers to proceed, ending its environmental impact assessment and the associated public comment period.

As a form of mobilization against the DAPL, a divestment movement campaign is taking place around the world.  The campaign #DeFundDAPL invites people to withdrawal their money for the list of banks  which are funding the Dakota Access Pipeline in a direct or indirect way.

After the Trump decision, in a symbolic gesture, the protesters set fire to their own camp. “People have said their last prayers, and offered cedar to the sacred fire and are also burning these structures we have ceremonially built, so they must be ceremonially removed,” Vanessa Castle of the Lower Elwha Klallam tribe. 

update: 

After four years of legal struggle in July 2020, a judge ordered Dakota Access pipeline to shut down. According to Earth Justice, "That ruling found that the U.S. Army Corps of Engineers had violated the National Environmental Policy Act (NEPA) and glossed over the devastating consequences of a potential oil spill when it affirmed its 2016 decision to permit the pipeline. The court ordered the Corps to re-examine the risks of the pipeline and prepare a full environmental impact statement, but left open the question as to whether pipeline operations would be halted as a legal remedy pending further briefing.  After carefully analyzing the seriousness of the government’s legal violations, and the potential impacts on the Tribe and third parties, today’s decision concluded that shutting down the pipeline was necessary" [1]

-A underground pipeline across both sides of Lake Oahe in North Dakota.

-The pipeline is planned to carry 470,000 barrels per day (75,000 m3/d) of crude oil "based on contractual commitments to date".[11] The capacity may be increased up to 570,000 barrels per day (91,000 m3/d)

-According with the company, Lake Oahe already contains eight other pipelines uneventfully operating adjacent to the path of the Dakota Access Pipeline, as well as one high-voltage electric transmission line.

-DAPL crosses at least 95 feet below the bottom of Lake Oahe, and at points, up to 115 feet below.

-The steel pipeline, developed and majority owned by Energy Transfer Partners, would connect the Bakken and Three Forks oil production areas in North Dakota to an existing crude oil terminal and pipeline terminus in Illinois.

-The entire project consist in 1,000-mile-long, 30 inches in diameter, it could transport an estimated 470,000 to 570,000 barrels of oil per day.

-The project, which traverses four states, is 92 percent complete overall and 99 percent complete in North Dakota.

-According with the company the Project will create 40 permanent jobs and 8,200 to 12,000 temporary jobs