>My impression is that individualism was a relatively marginal ideology
>until the government-sponsored explosion of the suburban sprawl in 1950s.
Depends on what you mean by individualism? Ever read any of the 19th century American classics, like Emerson, Thoreau, or Melville (who made merciless fun of the transcendentalists)? "I am an endless seeker with no past at my back. I unsettle all things," said Emerson. "Are they my poor?," asked Emerson.