206. Jeffery Hildebrand
A former Exxonmobil geologist, Hildebrand cofounded Hilcorp in 1989 and later bought out his partner for $500 million. By specializing in squeezing more oil and gas out of mature fields, he has built Hilcorp into the nation’s biggest privately owned oil company, with operations in Texas, Louisiana, Alaska and Ohio, where regulators have blamed his drilling for a series of earthquakes. Hilcorp has cooperated with officials. He teamed up with Carlyle Group in April to buy Conocophillips’ gas fields in Colorado and New Mexico for $3 billion. He owns a 957-acre ranch near Aspen that once belonged to John Denver.