Traveling post office IN GB

The first mobile post office was the Traveling Post Office (TPO) in

Great Britain. It was a mail train where they sorted mail en route, starting in 1838 - two years before the first self sticking postage stamp, The Penny Black. By 1963, there were 49 mail trains, where one to five TPO cars would be attached to passenger trains. TPOs were no longer used after early, 2004. The US version of the TPO was the Railway Post Office (RPO). At the height of the RPO, they were used in over 9,000 train routes, covering more than 200,000 route miles. The RPO was no longer used after 1977. There were also boat post offices, used in inland areas, such as the Seattle to Alaska region, inland lakes, Puerto Rico, and the Canal Zone. The boat post offices were no longer used after 1978. The RPO also used streetcar (electric) post offices from the late 1800s to early 1900s in many interurban areas, such as NYC, Boston, Chicago, San Francisco, Seattle, Washington D.C., and many other cities. The American Philatelic Society has published monographs regarding streetcar RPO routes.