Denison, Iowa, is as close to the heart of Middle America as it gets. The hometown of Donna Reed, Denison has adopted "It's a wonderful life" as its slogan and painted the phrase on the water tower that hovers over everything in town. And in many respects, life is pretty good here: it's a quiet town, a great place to raise children; the crime rate is low, the schools strong. It's home to the county's only Wal-Mart and a factory that does a booming business in antiterrorism barriers. For outsiders looking in, there is something familiar and comforting about Denison -- it conforms to the...