In order to safely transport oil to central Canada, a pipeline was proposed to connect the relatively secure Port of Portland in Maine with refineries in Montreal.

This rail line was built in the 1850s by the Atlantic & St. Lawrence Railroad which was purchased by the Grand Trunk Railway shortly after completion.

The Grand Trunk Railway encountered financial difficulties after World War I, and the company was nationalized by the Government of Canada in 1923 with its properties merged into the CNR.

[7] The pipeline extends 236 miles (380 km), 3 feet (0.91 m) beneath the surface, and has several pump stations distributed throughout the line.

The "Waterfront Protection Ordinance" aimed to ban future Canadian oil sands products from a reversed pipeline from being exported through the city's port.

Tom Hardison, vice-president of the Portland Pipe Line Corp., characterized it as a "biased process" and a "vote against jobs, energy and the waterfront".

[15] The Bangor Daily News had reported that "while several cities and towns along the pipeline have adopted nonbinding resolutions protesting the movement of the bituminous oil through their communities, the South Portland ordinance is viewed as the only measure that could actually prevent it.

"[11] Danielle Droitsch, of the Natural Resources Defense Council, said the Clear Skies Ordinance would be "very significant" in the fight against oil sands bitumen.

The city received a letter from the American Petroleum Institute, a major lobby group, indicating that vigorous legal challenges would be made to overturn it.

[16] In February 2015, Portland Pipe Line Co. (PPLC) filed a lawsuit in U.S. District Court to overturn the ordinance as being unconstitutional, and interfering with interstate and international trade.