Most of the photos on this site were extracted from reference images (high-resolution tiffs, 20 to 200 megabytes in size) from the Library of Congress research archive. (To query the database click here.) Many were digitized by LOC contractors using a Sinar studio back. They are adjusted by your webmaster for contrast and color in Photoshop before being downsized and turned into the jpegs you see here.

May 25, 1923. "Shrine post office." Set up for the big convention of Masonic orders held that year in Washington, D.C. National Photo glass negative. View full size.
The truck is a Packard. The year is more difficult to determine but probably around 1915.
Note the massive grille guard, removable front window, side curtains, and one beat up front fender.
Up until the big financial crises, the USPO used a big van to go to events and it was a real post office on wheels, having retired 10 plus years ago, I just wonder if that service also has been curtailed also.
Not unlike the USPS mobile sales vehicles found on the streets in some of our cities,

actually deliver mail to Zouaves?
Today's Top 5