TC PipeLines, LP (the Partnership) acquires, owns and participates in the management of energy infrastructure businesses in North America. Through the Company�s pipeline systems it transports natural gas in the United States. The Partnership is managed by its general partner TC PipeLines GP, Inc. (General Partner), which is an indirect, wholly owned subsidiary of TransCanada. Through its subsidiaries, TransCanada owns an approximately 33.3% interest in the Company, including a 31.3% limited partner interest and an effective 2% general partner interest held by its General Partner. It has ownership interests in four natural gas interstate pipeline systems, which can transport approximately 8.9 billion cubic feet per day of natural gas. All of its pipeline systems are operated by subsidiaries of TransCanada. On May 3, 2011, the Company acquired 25% membership interests in each of Gas Transmission Northwest LLC (GTN) and Bison Pipeline LLC (Bison) from subsidiaries of TransCanada.