The Trump administration reached a milestone this week in its plan to open a pristine part of Alaska to oil and gas development with the release of a final report on the environmental impact of the plan.

The report keeps the Interior Department on track to auction leases for the right to drill in the coastal plain of the Arctic National Wildlife Refuge before the end of the year, a long-stated administration goal. Having drilling rights in the hands of oil companies would make it more difficult to stop development in the refuge should Democrats take either the White House or Senate and keep control of the House in the 2020 elections.

Here’s a look at the issues and what has happened so far.

What’s at stake?

The Arctic National Wildlife Refuge is the largest remaining expanse of pristine land in the United States, an area the size of South Carolina that is largely devoid of human activity and home to migrating birds, polar bears, caribou and other wildlife.

Under a 1980 law, Congress left the possibility that 1.5 million acres — about 8 percent of the overall refuge — along the Arctic Ocean coast could be opened to oil and gas development. But for decades, Democrats, environmentalists and some Republicans derailed efforts to allow oil exploration in the area.