Von Braun said we could've put a man on Mars back in the '60s. He had all types of ideas that would've worked but were incredibly hard to do (ie funding, materials, workers, etc). He had ideas for space elevators, space stations (like serious space stations - not ISS), moon bases, and even a mars base. So it's been here quite awhile.
I do wonder when we'll finally just say "hell, lets make a moon base!". If only there were some resources on the Moon that would be very valuable like the movie Moon!