Where are iCloud data servers located?

I'm guessing/hoping iCloud does not use Amazon's S3 for storing iCloud data (such as pictures, documents, etc). I was wondering if anyone knew where the data center(s) were physically located? Given the amount of personal data we have (pictures, videos, etc) I'd like to make sure I've got my data saved in different physical locations should something happen to one of the major cloud services. Thanks for any help!