I listened to some of How the States Got Their Shapes on the drive today. I was fascinated by the history of West Virginia -- a state that exists because of Civil War opportunism. How physical borders are negotiated is a great segue into how other kinds of borders are negotiated in families, sects, corporations, etc. Great source of projects for a high school, eg "Why is South Kingstown the shape it is?" or "Why does the Chariho school district exist?".