When I think about this question, I'm mainly thinking about sci-fi books, like Robert Heinlein, and Ray Bradbury's The Martian Chronicles. Visions of skyscrapers and flying-cars - Tomorrowland. Was the 20th century the only instance in history of such imagination, or have there been other times when people dreamed of such a drastically different world? If so, when? And, what encourages a culture to dream like we once did? Was it simply brought about by the industrial revolution and huge advances in science in the early 20th century? Did the wars of the early 20th century play any role in these technologically-utopian dreams?

EDIT: Also, Star Wars and Star Trek come to mind.

EDIT 2: Also, Isaac Asimov.