I think it's well worth your time to view the video of the American Experience 1930s episode on the building of "Hoover Dam." It's available online at
http://www.pbs.org/wgbh/americanexperience/hoover.
A few of the things that struck me:
What a monumental feat, and it was completed about 2 years before the projected completion date.
Towards the end of project, when they were actually building the dam (after building tunnels to force the Colorado River to go around the dam site), they employed 5000+ workers, many who didn't have technical skills, to work 24/7 on the most ambitious man-made structure to that point.
The government hired an architect to convert the structural design into an aesthetically-pleasing monument with thousands of details, including Navajo-inspired designs on the floor. Some of the details they showed in this episode where amazing.
The men who worked on the project worked in unsafe conditions, sometimes in 130 degrees heat.
When FDR became President, he required the project to hire more Black Americans, although they were still segregated with separate living areas, separate trucks to deliver them and separate water buckets.
The workers and their whole families lived in a nearby town that was created almost overnight once the actual building of the dam took place. Prior to that, the families lived in the desert, some even without tents.