The amazing engineering marvel eventually called Hoover Dam was built from 1931-35, right smack dab in the middle of the Great Depression. Probably helped that desperate workers, many first- and second-generation Americans, came from all over the country to snap up the jobs. It was finished two years ahead of schedule.
It's a pretty amazing feat. How they diverted the water by blasting tunnels into the rock, how they manufactured parts onsite because they were too big to truck in, the working conditions, the amount of concrete used (a world record at the time), and so much more - all boggle my mind.
In the photo here, check out the line of cars snaking down from Arizona to cross into Nevada. It's a Friday and everyone's headed for Las Vegas. It'll take the cars at the top nearly an hour because of security measures adopted after 9/11. (Trucks must take an alternate route through Laughlin.) A bypass road is being constructed over the canyon and is scheduled to be done in November.