Perhaps many on SCF have already know this, but in going into some of the links on the Smithsonian's National Postal Museum web site, I found these 223 classic photos of US Mail Service history quite interesting. For those who have not seen them, I thought I'd share the link:
http://arago.si.edu/flash/?tid=2028018|s1=2Unfortunately the link doesn't go directly to the photo archives I am referring to so when you click on the link you must then click on the "down arrow" and select "photographic archives" to view.