As of 2015, the Keystone XL pipeline is owned by TransCanada Corporation through its subsidiary, TransCanada Keystone Pipeline, LP, according to TransCanada. TransCanada trades on the New York and Toronto stock exchanges as TRP.
TransCanada Keystone Pipeline, LP began as a partnership between TransCanada and ConocoPhillips to transport crude oil from Canada into the United States. In 2009, TransCanada reached an agreement to acquire ConocoPhillips' ownership in the partnership, leaving it the sole owner, reports Pipeline & Gas Journal. TransCanada Keystone Pipeline, LP is a subsidiary of TransCanada PipeLines Limited, which is itself a subsidiary of TransCanada Corporation, according to Bloomberg. The subsidiaries do not trade on the stock exchange.