In 2008, TransCanada, a Canadian oil company, proposed an extension of their existing Keystone Pipeline called the Keystone XL Pipeline. The proposed extension would reach from Canada to the Gulf of Mexico. In 2010, the Canadians approved the extension.
Since the proposed pipeline crosses an international boundary, the approval of the Obama Administration is required. In 2011, President Obama ordered a U.S. State Department review of the proposed extension. The southern portion of the pipeline from Cushing, OK to the Gulf Coast is already operating. This debate centers on the northern portion of the Keystone XL Pipeline.
Since 2011, the proposed northern extension of the Keystone XL Pipeline has become a divisive political issue with environmentalists who oppose the pipeline extension citing the climate costs of extracting the oil sands the pipeline would transport and its supporters citing the economic, energy, and employment benefits of the pipeline.
In 2015, both chambers of the Republican controlled U.S. Congress passed a bill forcing the approval of the pipeline extension. Subsequently, President Obama vetoed the bill.