In 2010, coal-fired power plants represented 45% of the electricity generated in the United States and oil a smaller amount, 1%. Combined together they are the dominant air polluters and facing tough new restrictions from the EPA.
Unfortunately, they have a few years to clean-up and that doesn’t help if you live in one of the toxic twenty states. Visit the previous link to see how your state compares, or scan this map to see if any of the polluting power plants are close to you.
Coal and Oil-fired power plants in the United States, 2010
There is also a Google Earth feature that allows you to find power plants where you live.