For years, Cushing, Okla., has been on the receiving end of a 500-mile pipeline funneling oil from the Gulf of Mexico to the American heartland.
Starting this weekend, that pipeline will start moving crude in the other direction. That flow reversal could soon have implications at gas pumps around the country.
"For 40 years, crude oil flowed north," says Philip Verleger, a visiting fellow at the Peterson Institute for International Economics. "Today, oil flows south. It's as if we turned the world upside down."