American cities all but lost their street life in the last decades of the twentieth century; anybody walking around downtown Philadelphia or Boston or Chicago after five in the afternoon found the streets deserted and dangerous. Today, in various forms, street life is returning. One can walk down Michigan Avenue in Chicago or Walnut Street in Philadelphia long after dark and find the place throbbing with activity and nearly always safe. American cities today are experiencing a renaissance of street life, returning to the dynamics of Europe’s early-twentieth-century cultural epicenters.