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”.