According to this posting, the contract between the National Archives and a private contractor for digitization of materials at NARA has terms of service that limits access to adults-only. “You have to be 18 to get an account and under no circumstances may anybody under 13 be allowed to look at archival documents.”
Also, access to the images at http://www.footnote.com/nara.php requires a paid membership or you can purchase documents at $1.99 per page.
The National Archives receives a copy of all the digital media for their archives, but the contract prohibits the Internet Archive (or anybody else for that matter) from having a copy of that data.
It is amazing to me how often the government goes down the road of trying to privatize public information.