http://www.transcanada.com/5951.html
media advisory that 75% of the pipeline would be made in USA with US steel. I would assume this equates to the 75% of the line that sits in the USA. as mentioned in this article only 40% of the actual construction remains; edit just re-read article and it was only 50% manufactured in USA.
http://www.npr.org/2014/11/17/364727...l-oil-pipeline