Not an RPO in the truest sense of the word, but still recognized by the USPS since 1961:
Quote:
In 1961, the Washington Park and Zoo Railway became one of the first recreation railroads to have its own cancellation stamp. With the demise of the Railway Post Office, the zoo railway is the last operating United States railroad with its own authorized railway postal cancellation to continuously offer mail service.
Posted 02/10/2012 10:06 am
