Loup County, Neb., the poorest county in the nation, is down to 712 people-a third of the population it had nearly a century ago. A four-bedroom house goes for $30,000. But building a life is much harder. In Loup County, what rides on the unrelenting winds are symptoms of despair that have taken hold there and across a large swath of rural America.

It could be Chemung County in upstate New York, which lost people and jobs even in the boom of the 90's. Or Bighorn County, Wyo., where some high school seniors say their only choices are to move out…