This Railway Post Office-SP5132 train car built in 1923 was used by Southern Pacific Railroad to sort and deliver mail throughout the pacific northwest. Rumored to be the only restored "R.P.O.",(rail
File:BLW Post Office (London) Railway (Mail Rail) Car (2).jpg - Wikimedia Commons
Railway Mail Crane | National Postal Museum
The birth of the Railway Post Office in 1869 - Farm and Dairy
A Day in the Life of a Railway Post Office Clerk | National Postal Museum
L&N #1100 Railway Post Office Car Program - Steamtown National Historic Site (U.S. National Park Service)
Railway post office
FreightWaves Classics: Railway post offices moved the mail across country - FreightWaves