This episode looks at America's most controversial cultural territory - the interstitial America of small towns and trailer parks. As his road trip takes him from Iowa to Tennessee, Waldemar Januszczak discovers how this much-maligned territory had an immensely beneficial impact on American art. From the Regionalist brilliance of Grant Wood to the small-town alienation of Edward Hopper to the spooky Dust Bowl symbolism of Alexandre Hogue, interstitial America inspired much that was great. The film culminates in the brilliant assemblages of David Smith, the leading sculptor of abstract expressionism.