Under Article I Section 8, Clause 7 of The Constitution of the United States, the Congress has the power “To establish Post Offices and post Roads“
So far as I know, “post roads” continued as the fundamental means of identifying a place for the delivery of mail until A.D. 1963 when they were supplanted by addresses associated with Zip Codes. It’s not clear to me whether “post roads” still exist. Although they are unused and almost unremembered, I suspect that “post roads” are still available if you care to use them to address your mail. Technically, “post roads” would seem to have been abandoned and unused for almost 50 years. Constitutionally, Congress not only has the power, they would seem to have the duty to “establish” and maintain “post roads”.
While searching for something else in the Revised Statutes of A.D. 1873-1875, I spotted The Revised Statutes of the United States relating to Post Roads passed at the First Session of the 43rd Congress, 1873-’74. With a title as catchy as that, who could resist peeking inside?
So I started thumbing through the pages and first thing I saw was the heading on page 3: “IN THE STATE OF ALABAMA” followed by 10 pages listing “post roads” in that State. And then on page 14 I read: “IN THE STATE OF ARKANSAS” followed by 7 pages listing “post roads” for that State.
The suspicion came almost instantly: The “post roads” are located within the States of the Union. The Zip Code addresses are located within the “territory” of “this state”. Under Article 1.8.7, the power and obligation imposed on Congress to establish “post offices” and “post roads” had to apply within the States of the Union. Given that, under Article 4.3.2, Congress had unlimited power to do virtually whatever it wants in the “territories,” Congress has the power to ignore “post roads” and instead establish Zip Code addresses within the “territories”.
If that conjecture is correct, and if you want to establish your presence within one of the States of the Union (rather than “in this state”/territory), you might do well to determine if your domicile is located on a “post road” and begin to use the “post road” as part of your “address” rather than a Zip Code.