Keystone XL Pipeline

Ending a process that has lingered for much of his time in the Oval Office, President Obama announced Friday that the U.S. has rejected TransCanada's application for a permit to complete the Keystone XL pipeline.

After spending years as a political football in the U.S., the Keystone XL pipeline's would-be builder is now asking for a timeout in the review process. Why now? Changing politics in the U.S. and Canada, falling oil prices and mounting pressure from environmentalists have marked a turnaround for the company, which had pushed for approval of the project, and its supporters.

Here are five things to know about where the pipeline stands now:

1. Geography gives the U.S. government a say

Updated at 5:04 p.m. ET

The Senate in a bipartisan 62-to-36 vote approved Thursday the Keystone XL pipeline project, setting up a faceoff with the White House, which has threatened a presidential veto.

Nine Democrats joined 53 Republicans to pass the measure, which now must be reconciled with a version passed last month by the House. The Senate vote is also not enough to override a presidential veto.

Northwest lawmakers voted along party lines as the U.S. Senate voted Tuesday to reject a plan to approve the Keystone XL oil pipeline.

Fourteen Democrats voted with all 45 Republicans in the Senate to approve it, but the plan was one vote shy of the minimum needed to send the measure to the president. 

Steve Liptay Photo

This Saturday, environmental activist and author Bill McKibben will lead a rally against fossil fuel exports and the Keystone XL pipeline in Seattle. 

Known as one of the first voices to warn of the dangers of global warming, McKibben is on tour with his new book, Oil and Honey. He is also the founder of an international organization called, which he created to fight climate change. 

McKibben says 350 is "the most important number in the world, but nobody knew it until 2008, when Jim Hansen and his team at NASA published a paper saying we now know enough about carbon to know how much in the atmosphere is too much."