They worry the project will disrupt cultural artefact's and hurt drinking water sources on the Standing Rock Sioux's nearby reservation and farther downstream because the pipeline will cross the Missouri River.
The Texas-based company building the pipeline, Energy Transfer Partners, insists the project is safe.
Protesters have been crowdsourcing to help fund their fight which has since topped a staggering US$1million.
The fund is among several cash streams that have provided at least US$3 million to help with legal costs, food and other supplies to those opposing the nearly 1930km pipeline.
The tribe is fighting the pipeline's permitting process in federal court.
However, it appears the pipeline has some top level support in the form of presidential candidate Donald Trump who owns stock in the company building the Dakota Access oil pipeline across the Midwest.
Trump's 2016 federal disclosure forms, filed in May, show he owned between $15,000 and $50,000 in stock in Texas-based Energy Transfer Partners.