The possibility of either a deliberate EMP attack or a solar storm taking out the power grid seems to be back in the news. For a worst case scenario, I would recommend the book "One Second After" by William Forstchen. However, this book presupposes that the US was hit by three EMP weapons simultaneously (to blanket the entire country), and by enemies who also took out Europe, Japan, Australia and anyone else who could have helped America rebuild. It also supposes that all post 1970's vehicles and electronic equipment would be permanently destroyed. But what about the somewhat more likely possibility of a limited EMP attack? What if, for example, a terrorist group launches one nuke that triggers an EMP effect over half the eastern seaboard? Now, the good news would be that most of the food growing regions of the country would be safe, we'd still have the infrastructure to deliver food and drinking water to the east coast, the direct loss of life would be in the thousands rather than in the millions. The bad news? The entire US economy would be wiped out. Tens of millions of people would be in danger of dying if they weren't immediately helped by the rest of the country. It might take years to get electric service completely resorted to the east coast. Untold economic infrastructure (think every small business on the east coast that depends on a computer) would be wiped out. Millions of displaced workers would swamp the rest of the country, hoping that any state that still has electricity would also have jobs. Those remaining in east coast cities would face daily riots. Almost all overseas military operations would have to be shut down, because the troops would be needed at home. Think hurricane Katrina x 10. Now, all this isn't nearly as scary as Forstchen's prediction of 90% of the population dying within a year. But, even aside from a US nuclear retaliation, any group the killed 90% of the US population would face opposition from everyone else on the planet who was afraid that they might be next. Whereas knocking out half of the US power grid would probably be applauded by the United Nations (just as soon as they found another air conditioned building to meet in).