I thought about this when I visited the Hoover Dam. The audacity of the thing and sheer impossibility of doing anything remotely like it in today's America makes it seem like a relic from an ancient civilization. It felt like visiting the pyramids in Egypt.
The development of the atomic bomb also amazes me. I get a kick out of this video setting up the first test: https://www.youtube.com/watch?v=J7CmcsOubZ8 No hard-hats No shirts Free climbing tower with no safety lines Cigarette hanging from mouth No way they could ever pull this off today. No way the Apollo program could be pulled off either.
It is no wonder "farmer" is one of the most dangerous occupations in the US. They're the last to be impacted by health and safety regulations.