Before the Hamptons perfected the choreography of linen, rosé and strategic nonchalance, the East End smelled of salt, turpentine, wet earth and artistic mutiny. Certainly, the light was ravishing. Yet painters came for something more dangerous: distance from Manhattan, permission to fail extravagantly and the possibility that American painting might finally grow vast enough to tear open the beautiful, terrified interior of its age. In many ways, the moment was almost violently precise. By 1945, Europe had been ravaged by war, while New York was becoming modern culture’s gravitational center. The old pictorial languages seemed indecently composed beside the Holocaust,...