(CNN) — On March 13, the Biden administration approved the controversial Willow Project in Alaska.

ConocoPhillips’ massive Willow oil drilling project on Alaska’s North Slope moved through the administration’s approval process for months, galvanizing a sudden uprising of online activism against it, including more than one million letters written to the White House in protest of the project and a Change.org petition more than 3 million signatures.

Here’s what to know about the Willow Project.

What is the Willow Project?

ConocoPhillips’ Willow Project is a massive and decadeslong oil drilling venture on Alaska’s North Slope in the National Petroleum Reserve, which is owned by the federal government.

The area where the project is planned holds up to 600 million barrels of oil. That oil would take years to reach the market since the project has yet to be constructed.

Who started the Willow Project and when?

ConocoPhillips is a Houston-based energy company that has been exploring and drilling for oil in Alaska for years. The company is the only one that currently has oil drilling operations in Alaska’s National Petroleum Reserve, though its two operating projects are smaller than Willow would be.

Willow was proposed by ConocoPhillips and originally approved by the Trump administration in 2020. ConocoPhillips was initially approved to construct five drill pads, which the Biden administration ultimately reduced to three. Three pads will allow the company to drill about 90% of the oil they are pursuing.

The Biden administration felt its hands were tied with the project because Conoco has existing and valid leases in the area, two government sources told CNN. They determined that legally, courts wouldn’t have allowed them to fully reject or drastically reduce the project, the sources said. If they had pursued those options, they could have faced steep fines in addition to legal action from ConocoPhillips.

When could Willow oil drilling begin?

Now that the Biden administration has given the Willow project the green light, construction can begin. However, it is unclear exactly when that will happen, in large part due to impending legal challenges.

Earthjustice, an environmental law group, is expected to file a complaint against the project soon and will likely seek an injunction to try to block the project from going forward.

Environmental groups and ConocoPhillips are each racing against the clock. Construction on Willow can only be done during the winter season because it needs ice roads to build the rest of the oil project’s infrastructure — including hundreds of miles of roads and pipelines and a processing facility. Depending on the weather, the Alaska’s winter season could end sometime in April.

If environmental groups secure an injunction before then to stop or delay the project, it could delay construction for at least a year. And since the project needs to be fully constructed before the oil can be produced, it could take years for the oil pumped out of Willow to reach the market.

What could the legal arguments be against Willow?

The Willow Project will almost certainly face a legal challenge. Earthjustice has told CNN it is preparing a complaint, and it has already started laying out their legal rationale, saying the Biden administration’s authority to protect surface resources on Alaska’s public lands includes taking steps to reduce planet-warming carbon pollution — which Willow would ultimately add to.

“We and our clients don’t see any acceptable version of this project, we think the analysis is unlawful,” Jeremy Lieb, an Alaska-based senior attorney for Earthjustice, previously told CNN.

Who supports the Willow Project?

The state’s lawmakers say the project will create jobs, boost domestic energy production and lessen the country’s reliance on foreign oil. All three lawmakers in Alaska’s bipartisan congressional delegation met with President Joe Biden and his senior advisers on March 3, urging the president and his administration to approve the project.

A coalition of Alaska Native groups on the North Slope also supports the project, saying it could be a much-needed new source of revenue for the region and fund services including education and health care.

“Willow presents an opportunity to continue that investment in the communities,” Nagruk Harcharek, president of the advocacy group Voice of the Arctic Iñupiat, told CNN. “Without that money and revenue stream, we’re reliant on the state and the feds.”

Who opposes the Willow Project?

Other Alaska Natives living closer to the planned project, including city officials and tribal members in the Native village of Nuiqsut, are deeply concerned about the health and environmental impacts of a major oil development.

In a recent personal letter to Interior Secretary Deb Haaland, Nuiqsut Mayor Rosemary Ahtuangaruak and two other Nuiqsut city and tribal officials said that the village would bear the brunt of health and environmental impacts from Willow. Other “villages get some financial benefits from oil and gas activity but experience far fewer impacts that Nuiqsut,” the letter reads. “We are at ground zero for the industrialization of the Arctic.”

In addition, a surge of online activism against Willow has emerged on TikTok in the last week — resulting in over one million letters being sent to the Biden administration against the project and over 2.8 million signatures on a Change.org petition to halt Willow.

Would the Willow Project be bad for the climate crisis?

By the administration’s own estimates, the project would generate enough oil to release 9.2 million metric tons of planet-warming carbon pollution a year — equivalent to adding 2 million gas-powered cars to the roads.

“This is a huge climate threat and inconsistent with this administration’s promises to take on the climate crisis,” Jeremy Lieb, an Alaska-based senior attorney at environmental law group Earthjustice, told CNN. In addition to concerns about a fast-warming Arctic, groups are also concerned the project could destroy habitat for native species and alter the migration patterns of animals including caribou.

Willow advocates, including Alaska lawmakers, vow the project will produce fossil fuel in a cleaner way than getting it from other countries, including Saudi Arabia or Venezuela.

“Why are we not accessing from a resource where we know our environmental track record is second-to-none?” Republican Sen. Lisa Murkowski of Alaska said during a recent press conference.

Did approving the Willow Project break a campaign promise Biden made?

Yes. During his 2020 presidential campaign, Biden vowed to end new oil and gas drilling on public lands and waters — which he initially carried out as part of an early executive order.

However, the drilling pause was struck down by a federal judge in 2021, and since then the Biden administration has opened up several areas for new drilling. Several of these new oil and gas drilling areas have been challenged in court by environmental groups.

The Willow Project has been approved. Here’s what to know about the controversial oil-drilling venture