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 ]