His overalls caked in mud, roughneck Brian Waldner wrestles with pipe as North Dakota's new horizon unfolds around him. (Related: "Oil Train Revival: Booming North Dakota Relies on Rail to Deliver Its Crude")

North Dakota, once a sleepy backwater of the petroleum industry, this year surpassed Alaska as the number two oil producer in the United States. The gush of North Dakota crude has helped lift U.S. oil production to its highest level in 14 years, and has the United States on track to regain its spot as the world's top energy producer within five years. (Related: "U.S. to Overtake Saudi Arabia, Russia as World's Top Energy Producer")

It's all due to hydraulic fracturing, or fracking, a new combination of old technologies that has yielded astounding results. Using high-pressure water, sand, and chemicals, the energy industry has been able to force abundant oil and natural gas production from underground shale formations around the United States. (See interactive, "Breaking Fuel From Rock.")

Controversy abounds over fracking's impact on land, water, and air. But there's no question it has boosted energy resources and local economies. (See Special Report, "The Great Shale Gas Rush")

Nowhere is this more visible in North Dakota, which has the lowest unemployment rate in the United States (3.1 percent.)

As workers labored in October on this True Company rig outside Watford City, North Dakota set a new one-month record for issuance of drilling permits, 370, up tenfold from just five years ago. (Related: "Shale Oil Boom Takes Hold on the Plains")

—David LaGesse

This story is part of a special series that explores energy issues. For more, visit The Great Energy Challenge.

Pictures: Bakken Shale Oil Boom Transforms North Dakota

Thanks to a new combination of old technologies, oil production in North Dakota is exploding, drawing thousands of workers to the state's thriving oil patch.