The dissertation traces the legislative and judicial history of the constitutional grant allowing Congress to create post offices and post roads, and analyzes how that authority has been expanded through statutes and court rulings. It examines congressional powers to establish postal facilities and routes, regulate mail carriage, and punish postal crimes, while assessing constitutional limits such as freedom of the press and protections against unreasonable searches. The study reviews state attempts to interfere, federal efforts to control transportation and communications infrastructure including railways, telegraph and telephone systems, and the use of exclusion from the mails as a regulatory device, weighing doctrinal developments alongside practical implications.