Modeling RPO Mail Service on US Railroads
Check out these three articles on how US railroads handled the mail:
http://www.archives.gov/publications/pr ... ail-1.html
http://www.archives.gov/publications/pr ... ail-2.html
http://www.archives.gov/publications/pr ... -side.html
http://www.archives.gov/publications/pr ... ail-1.html
http://www.archives.gov/publications/pr ... ail-2.html
http://www.archives.gov/publications/pr ... -side.html