On LinkedIn, there's a recruiter I was acquainted with before he went to Amazon, and I notice (on my news feed or whatever it's called) he's always looking for people for cleared positions these days. Not sure why.
With the recent NSA contract win, there might be a 3rd cloud to run.
This highlights they cater to every US classification level:
https://aws.amazon.com/government-education/government/
This announces their secret region, and references their top-secret one.
https://aws.amazon.com/blogs/publicsector/announcing-the-new...
Note: you might have to dig to find the non-US government classified clouds. They are documented in plain sight though.
Left as an exercise for the reader.
[ edited to add links ]