Proponents of the pipeline say it will lessen dependence on foreign oil while creating jobs and growing domestic industry. However, many Americans, and primarily Native Americans, are furious about Trump's latest executive order.

Barack Obama killed the Keystone XL pipeline in November 2015, stating it wouldn't have helped lower gas prices or create that many jobs. He also said the long-term contribution to climate change — possibly more than 22 billion metric tons of carbon pollution, according to Scientific American — wasn't worth the loss of America's global leadership on fighting emissions that exacerbate global warming.
"If we're going to prevent large parts of this Earth from becoming inhabitable, if not inhospitable [...] we have to keep some fossil fuels in the ground," Obama said.
Trump's televised revival of Keystone XL didn't mention its steep environmental costs, including the 54,000 square miles (140,000 square kilometers) of pristine Alberta wilderness that may be industrialized to feed it.
"We're not saying the project is good or bad. We're just saying the scale and severity of what's happening in Alberta will make your spine tingle," Robert Johnson, a former Business Insider correspondent, wrote after flying over the Canadian oil sands in May 2012.
Keep scrolling to see an updated version of Johnson's photo essay, which shows Canadian oil mining — a process in which tar-laden sand is dug from the ground and the oil is separated through a lengthy and messy process.
This story has been updated to include details about in situ extraction, which is different from the mining method and makes up about half of Canada oil sands production.
To get a look at the oil sand mines, we rented this Cessna 172, which the pilot was allowed to bring down to 1,000 feet. Through the open window we could see what really goes on in one of the most controversial places on the planet.

The Alberta oil sands are spread across more than 54,000 square miles but we're taking a look at just a small part of it. The red line is an approximate outline of the entire deposit — the green is where we'll be flying.