U.S. mail trucks lined up outside a Post Office sometime between 1909 and 1940. Today the USPS's 213,881 vehicles -- which is the largest civilian fleet in the world
-- drive more than 1.2 billion miles each year.
February 6, 2013 1:55 PM PST
Photo by: Library of Congress
| Caption by: James Martin
Conversation powered by Livefyre