§ 5003. Establishment of post roads

The following are post roads:

• (1) the waters of the United States, during the time the mail is carried thereon;
• (2) railroads or parts of railroads and air routes in operation;
• (3) canals, during the time the mail is carried thereon;
• (4) public roads, highways, and toll roads during the time the mail is carried thereon; and
• (5) letter-carrier routes established for the collection and delivery of mail.