In July, Reed took over the Fortune 500 energy services company with $9 billion in 2010 revenue. The industry veteran once served as president and CEO of Sempra's San Diego Gas & Electric and Southern California Gas. She also sits on the Halliburton board.
Boardroom battles and power plays shaped this year's U.S. list, which boasts eight new faces and -- surprise! -- a new No. 1.
