For many Americans, rural spots such as Vandalia are increasingly mysterious, drifting further and further away from larger cities in their values, politics and economics. Vandalia offers a unique viewing point. Like lots of Midwestern towns it is ringed by farms, has a fine, brick-built main street, and boasts a single high school and many churches (Vandalia has 18, or one church for every 300 permanent residents). But it stands out for its role in a sociological experiment of half a century ago, when its inner workings were studied by the writer Joseph Lyford. His book-length report, “The Talk in Vandalia”, prompted a local stink, admiring national headlines and a television film. Fifty years on, it offers a chance to trace the long-term forces buffeting such places.