Cars aren't pulled around by horses. Women aren't slimmed down by corsets. Men don't shine their hats with mercury. But the same fuel that's electrified our nation for over a century is still going strong.

Mega-utilities such as FirstEnergy Corp. (NYSE:FE) and American Electric Power Company (NYSE:AEP) continue to rely on this fuel for the majority of their electricity generation -- and they don't seem to be in any hurry to change.

Check out the following slideshow to discover which fuel we still use to turn on the lights, and why certain companies are as happy as ever to keep using it to pull their power.