ENERGY: King Coal's Return: Wealth and Worry

The U.S. has had one great piece of luck on energy. Hundreds of millions of years ago, the land was swampy and covered with plants. As they died, they fell under water, where there was not enough oxygen for them to decay completely. With geological change over the eons, these plants were tightly compacted, then compressed. The result became an almost mythical abundance of coal.

It provided the cheap energy that powered America's growth. The coal flowed in a steady black stream from the deep mines of Appalachia to fire the boilers of...