Harold Hamm

Fracking pioneer Harold Hamm runs Continental Resources, one of the nation's biggest independent oil companies.The 13th child of Oklahoma sharecroppers, he picked cotton barefoot as a child and started working at a gas station at age 16 to support his family.He eventually started his own trucking company hauling water to and from oilfields, then in 1971 took out a loan to drill his first well.In the 1990s he had the vision to use horizontal drilling and hydraulic fracturing in North Dakota's Bakken region, transforming the US oil industry.Today Continental produces more than 200,000 barrels per day, much of it from North Dakota's Bakken formation.Hamm, who has type-2 diabetes, has donated about $30 million to establish the Harold Hamm Diabetes Center at the University of Oklahoma.