Article I, Section 8, Clause 7:
[The Congress shall have Power . . .] To establish Post Offices and post Roads; . . .
The great question raised in the early days with reference to the postal clause concerned the meaning to be given to the word
establish – did it confer upon Congress the power to construct post offices and post roads, or only the power to designate from existing places and routes those that should serve as post offices and post roads? As late as 1855, Justice McLean stated that this power
has generally been considered as exhausted in the designation of roads on which the mails are to be transported, and concluded that neither under the commerce power nor the power to establish post roads could Congress construct a bridge over a navigable water. 1 A decade earlier, however, the Court, without passing upon the validity of the original construction of the Cumberland Road, held that being
charged . . . with the transportation of the mails, Congress could enter a valid compact with the State of Pennsylvania regarding the use and upkeep of the portion of the road lying in the state. 2 The debate on the question was terminated in 1876 by the decision in Kohl v. United States, 3 sustaining a proceeding by the United States to appropriate a parcel of land in Cincinnati as a site for a post office and courthouse.