Beneath the wheat and the cattle range of the west lies one of the largest oil accumulations in the lower forty-eight — the Bakken and Three Forks formations, a layer of oil-soaked rock some two miles down and only as thick as a house is tall. For decades it defied the drill. Horizontal drilling and hydraulic fracturing finally unlocked it, and North Dakota vaulted into the front rank of the nation's oil states.

Oil from Two Miles Down

Williston is the play's beating heart, a town that swelled almost overnight as the rigs multiplied across Williams and McKenzie counties. Truck traffic, housing, water, sand and steel all had to be conjured from a prairie that had known only farming, and the boom rewrote the map of the west in a decade.

From the almanac's reckoning:

• The Bakken and Three Forks formations lie about two miles beneath the surface.
• Horizontal drilling and hydraulic fracturing made the play economic.
• Williston sits at the center of Williams and McKenzie county drilling.

The play lives and dies by the price of crude, and the plains have learned to ride that wave — flush in the good years, sober in the busts. The almanac reckons the Bakken among the largest transformations the state has ever seen, for good and for ill.