Prudhoe Bay oil fields.
One of the largest oil fields ever discovered, Prudhoe Bay has been in production for over 30 years. The amount of oil being pumped through the 800-mile (1,287-kilometer) BP, ExxonMobil and ConoccoPhillips owned Trans-Alaska Pipeline has dropped to around 500,000 barrels a day in 2011 compared to 2 million barrels a day in the eighties, as output from onshore fields fall.