NASA: Powering down the last mainframe
This is a TechRepublic article (February, 2012) that is a reflection of the changing landscape of IT. There are other mainframe systems in use in government so they are not all being retired but for a number intensive operation like NASA to be at the stage where they are retiring their last mainframe computer it is symbolic of the end of an era.
NASA: Powering down the last mainframe (February, 2012)
http://www.techrepublic.com/blog/tech-manager/nasa-powering-down-the-last-mainframe/7368?tag=nl.e106