Alaska's Last Oil : The world is addicted to oil. But now the easy pockets of oil are gone and the race is on to find new sources. Nowhere is the battle more intense than in Alaska - source of nearly 15% of America's domestic production, and home to the nation's largest wildlife preserve, the Arctic National Wildlife Refuge, where companies are pushing to drill. EXPLORER travels back millions of years to see how oil was created, and looks to the future to ask how far we'll go to find every last barrel and at what cost.