Calgary-based TransCanada announced the news on its website Wednesday. At about 10:45 a.m. central time, the Gulf Coast Project began delivering crude oil to the pipeline company's refining customers.
"This is a very important milestone for TransCanada, our shippers and Gulf Coast refiners who have been waiting for a pipeline to supply oil directly from Cushing," TransCanada CEO Russ Girling said.
The 783-kilometre stretch of pipeline in the American South cost $2.3 billion to develop and construct. The 36-inch pipeline that can transport as much as 830,000 barrels of oil per day.
TransCanada was trumpeting the opening of the pipeline as a watershed moment on Wednesday, but the company still faces numerous hurdles getting the rest of the Keystone XL pipeline approved.
The remaining portion of the pipeline is still seeking final approval from the U.S. government. When and if it's completed, it will ship Canadian oil more than 1,800 kilometres from Hardisty, Alta., through six U.S. states to the Gulf of Mexico for refining and export.
Environmentalists have rallied against the project, urging U.S. President Barack Obama to stop its construction. But it's backers say it will be an economic boom for both countries and reduce North America's dependence on foreign oil from more hostile parts of the globe.