Here's a look at what's up with the pipeline and what lies ahead for its planned construction.
Right now, the Keystone Pipeline system
stretches more than 2,600 miles from Hardisty, Alberta,Canada east into Manitoba and then down to Texas, according to parent company TransCanada. That pipeline already functions and transports crude oil from Canada.
The proposed Keystone XL Pipeline, which would stretch from Hardisty down to Steele City, Nebraska, would complete the entire proposed system by cutting through Montana and South Dakota.
The idea is that it would carry crude oil from where it's produced to where it's refined, TransCanada's website says
Construction of the pipeline will create just 35 permanent jobs
Trump touted the approval as being a big job creator, and TransCanada CEO Russell Girling said the pipeline would create "thousands of jobs."
Many of those jobs will be temporary. A State Department report during the Obama administration found that 3,900 construction jobs would be needed to build the pipeline
if it were built in a year, or 1,950 jobs if it were to be built in two years.
And once it's built, operation of the pipeline would only need 35 permanent employees and 15 temporary contractors, according to that report.
However, the State Department report estimated that the pipeline would create 42,000 jobs directly and indirectly in business related to its completion, with a total of $2 billion in wages. That comes to an average of about about $47,000 in wages per job. .
But the fight is not yet over
Facing pressure from environmental groups, President Barack Obama vetoed legislation
that would have approved the project in February 2015. Trump now occupies the White House, but that pressure has hardly gone away.
Environmental groups are wary that the pipeline will rely on Canadian oil sands
, a dirtier form of oil that releases more greenhouse gases than standard oil extraction. In addition, environmentalist groups are wary that construction of the pipeline -- and a potential leak -- would impact sources of fresh water like the Ogallala Aquifer, which would be near the Keystone XL pipeline.
In a statement, Greenpeace USA Executive Director Annie Leonard said
the group would do "everything it can" to stop the Keystone XL Pipeline from coming to fruition.
"The world simply cannot afford to transport or burn the Canadian tar sands if we hope to have any chance at avoiding catastrophic climate change," Leonard said. "Keystone was stopped once before, and it will be stopped again."
Indigenous groups stand against the project
Similarly, Native American groups have argued that the pipeline would cut across their sovereign lands.
"Donald Trump should expect far greater resistance than ever before," said Tom Goldtooth, Executive Director of the Indigenous Environmental Network that prominently fought the Dakota Access Pipeline.
"We've stopped the toxic Keystone XL Pipeline once, and we will do it again," he said. "Indigenous nations stand united not just here in the U.S. but around the world. This fight is not over, it is just beginning."