America has a fascination with origin stories. Partly because the continent was populated by migrants who displaced or killed the indigenous people, it is tempting for historians to tell the American story through a particular movement or group. From Frederick Jackson Turner’s seminal work on frontier culture to Edmund Morgan’s books on the lasting influence of the Pilgrims, much effort has been spent on tracking the impact of subcultures on the way US society developed. At a time when there is much anger and hand-wringing over the outsized influence of a few business sectors — first bankin...