Lee Tillman took the reins of Marathon Oil in 2013 following nearly 25 years as an engineer and vice president at Exxon Mobil.

Marathon and its refining arm, Marathon Petroleum, had been split in 2011. His not-so-simple task was to take a formerly integrated oil company and turn it into a more profitable and leading exploration and production independent.

Fast forward to 2019 and Houston-based Marathon is now a U.S.-centric shale player focused primarily on Texas, New Mexico, Oklahoma and North Dakota.

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