> I think I read that Northern Virginia, USA has the highest data center density in the world. Mostly it is due to demand from US gov't, military, and spy agencies (like NSA).

That's where AWS us-east-1 is, i.e. the oldest AWS region where they got started to begin with. Google and Microsoft also have a large presence there. It's not just the US government, it's everybody, and it's not new.

> How did they do it?

Here's the US nuclear plant map, guess where a bunch of them are:

https://www.eia.gov/todayinenergy/detail.php?id=65104

The area around Virginia is also a major coal producer and when this was getting started it was a source of cheap electricity, but coal is quickly being replaced with natural gas via pipelines from the Gulf coast. Their current power mix is ~30% nuclear, ~12% renewables (solar) and almost all the rest natural gas.