Notable events in the dispute over the Dakota Access oil pipeline.
Dec. 2014 — Dallas-based Energy Transfer Partners applies to the federal government to build the 1,200-mile, $3.8 billion Dakota Access pipeline to carry half a million barrels of North Dakota oil daily through the Dakotas and Iowa to a distribution point in Illinois. The proposed route skirts the Standing Rock Sioux tribe’s reservation and crosses under Lake Oahe, a Missouri River reservoir in the Dakotas that serves as the tribe’s drinking water source.
April 2016 — Opponents establish a camp in southern North Dakota for peaceful protest. Camps in the area would later swell to thousands of people.
July 2016 — The Army Corps of Engineers grants pipeline permits at more than 200 water crossings. The Standing Rock Sioux sues. The Cheyenne River, Oglala and Yankton Sioux tribes later join as plaintiffs.
Aug. 10 — North Dakota authorities make the first arrests of protesters. The total eventually reaches 761 over more than six months. Those arrested include actress Shailene Woodley and Green Party presidential candidate Jill Stein, neither of whom ends up serving jail time.
Sept. 9 — U.S. District Court Judge James Boasberg in Washington, D.C., denies an attempt by the Standing Rock Sioux to halt pipeline construction. The same day, the Army, the Department of Justice and the Interior Department declare that construction bordering or under Lake Oahe won’t go forward pending further review.
Nov. 20, 21 — Authorities use tear gas, rubber bullets and water sprays on protesters who they say assaulted officers with rocks and burning logs at a blockaded bridge, in one of the most violent clashes of the protest. At least 17 protesters are taken to hospitals. One officer was injured when struck in the head with a rock.
Dec. 4 — Assistant Army Secretary for Civil Works Jo-Ellen Darcy declines to allow the pipeline to be built under Lake Oahe in part because she says alternate routes need to be considered. ETP accuses President Barack Obama’s administration of delaying the matter until he leaves office.
Jan. 18, 2017 — The Corps launches a full environmental study of the disputed Lake Oahe crossing that could take up to two years to complete. Boasberg rejects an ETP request to stop the study.
Jan. 24 — President Donald Trump signs an executive action to advance the pipeline’s construction.
Feb. 8 — The Army forgoes further study and grants an easement necessary to complete the pipeline. Crews immediately begin drilling under Lake Oahe.
Feb. 22-23 — Authorities clear out the last remaining holdouts in the main protest camps in southern North Dakota in advance of spring flooding season.
March 10 — Pipeline opponents rally in Washington, D.C., demonstrating outside the White House and Trump’s Washington hotel.
March 20 — ETP announces “coordinated physical attacks” along the pipeline. Authorities in South Dakota and Iowa confirm people apparently used a torch to burn holes through empty sections of the pipeline at aboveground shut-off valve sites.
April 4 — The pipeline leaks 84 gallons of oil at a rural pump station in South Dakota. Federal data released in May showed that the pipeline and a feeder line leaked more than 100 gallons of oil in North Dakota in separate incidents in March. All of the spills were cleaned up.
April 29 — North Dakota Gov. Doug Burgum asks Trump for a presidential disaster declaration to pave the way for federal reimbursement of protest policing costs. Trump later rejects the request.
May — Documents leaked to an online magazine show that TigerSwan, a private security firm hired by ETP, conducted an aggressive, multifaceted operation against protesters that included a close working relationship with public law enforcement.
June 1 — The pipeline begins shipping oil.
June 14 — Boasberg orders the Corps to do more environmental assessment of the pipeline’s impact on the Standing Rock Sioux. The Corps estimates the work will take until April 2018.
June 27 — North Dakota’s Private Investigative and Security Board sues TigerSwan for operating in the state without a license. TigerSwan says it’s the victim of a smear campaign.
Aug. 22 — ETP sues Greenpeace and other groups, alleging they disseminated false and misleading information about the project and interfered with its construction. ETP seeks damages that could approach $1 billion. Greenpeace says the suit is meritless.
Sept. 20 — North Dakota regulators approve an agreement settling allegations that ETP violated state rules during construction. It includes no fine and no admission of liability by the company.
Sept. 27 — Archambault is defeated in his bid for re-election as tribal chairman.
Sept. 28 — ETP gives North Dakota $15 million to help pay an estimated $43 million in protest policing bills. The state four days earlier had received a $10 million grant from the U.S. Justice Department for the same purpose.
Oct. 10 — The North Dakota Pipeline Authority says the pipeline boosted the state’s tax revenues by about $19 million in its first three months of operation.
Oct. 10 — U.S. District Judge Daniel Hovland in Bismarck, North Dakota, dismisses a lawsuit filed by twenty-one North Dakota landowners who alleged ETP and a consultant used deceit and fraud to acquire land easements.
Oct. 11 — Boasberg rules that the pipeline can continue operating while more court-ordered study is completed to assess its environmental impact on the Standing Rock Sioux.