Prudhoe Bay Oil Field, Alaska

This is the nation's largest conventional oil field, and the main reason for the creation of the Alaskan Pipeline, which starts here, and terminates in Valdez, Alaska, 800 miles away. With an estimated 13 billion barrels of recoverable oil, Prudhoe Bay is twice as large as the next largest conventional oil field (in east Texas). It is however just one of a network of oil fields in an area about 20 miles tall and 40 miles wide, the actively productive oil fields of the North Slope of Alaska. BP, ExxonMobil, and ConocoPhillips are the primary leaseholders. The area is bounded on the east by the Arctic National Wildlife Refuge, and to the west the mostly undeveloped National Petroleum Reserve. The field is now about 85% depleted: an estimated 2 billion barrels of recoverable oil remain in the field.