Imagine what would have happened in 1937 had the builders of the Golden Gate Bridge stopped half-way across the water separating the San Francisco peninsula and San Marin County because a bunch of feuding politicians couldn't agree to finish the job. Late-night comedians would still be making jokes about the giant diving boards into the Golden Gate strait. Two years ago this weekend, President Obama put himself in a similar position by endorsing construction of the southern leg of the proposed Keystone XL pipeline but delaying approval of the northern leg. Now it's up to Obama to tell the builders to finish the job.

The Keystone pipeline would carry oil produced from Canadian tar sands south to America's most advanced refineries on the Gulf Coast. These refineries are best-suited to refining the Canadian crude to satisfy the Environmental Protection Agency's increasingly complicated gasoline-blend formulas that are intended to minimize emissions throughout the nation's multiple climates and geographies.

What's been done so far has created thousands of jobs, boosted regional economic growth and helped alter the world's energy politics equation.

As Obama spokesman Jay Carney said the day before his boss delivered a significant speech endorsing the southern leg in 2012 in Cushing, Okla., "moving oil from the Midwest to the world-class, state-of-the-art refineries on the Gulf Coast will modernize our infrastructure, create jobs, and encourage American energy production."

What's been done so far in completing the Keystone leg from Cushing to Nederland, Texas, has created thousands of jobs, boosted regional economic growth and helped alter the world's energy politics equation. As TransCanada, the pipeline's main constructor, recently pointed out, “construction of the 487-mile crude oil pipeline involved more than 11 million hours of labor completed by 4,844 workers in the United States of America, more than 50 contracts with manufacturers and companies building the pipeline and equipment from across the U.S. It also includes the addition of 2.25 million barrels of new oil storage capacity at Cushing, Oklahoma.”

Construction industry unions like those representing welders working on the project are, understandably, enthusiastic about the work they've done on Keystone's southern leg and are impatient to get started building the northern leg. “These are really good paying jobs. They provide not only a good living wage, they provide health care and they also provide a pension,” Danny Hendrix of the Tulsa, Okla.-based Pipeliners Local 798 told the Associated Press in February 2013. “If the permits get approved, we'll start construction of the northern end immediately.”

There are also foreign policy reasons to finish Keystone, which is needed to help move increasing U.S. energy supplies. The fracking revolution in the U.S. energy industry has propelled the country to a point where it could soon become independent of foreign sources in the Middle East, South America and Russia. Vladimir Putin would have to think twice about further aggression in the Ukraine if he knew the U.S. was in a position to supplant Europe's dependence on Russia's Gazprom natural gas supplies. Since Gazprom is the key to Russian economic security, the prospect of U.S. companies becoming Europe's energy suppliers would seriously complicate Putin's ambition to restore the old Soviet empire from Cuba to Eastern Europe.