On July 26, 1775, the U.S. postal system was established by the Second Continental Congress, with Benjamin Franklin appointed the first postmaster general. Although no patents surround the creation of the postal service (the first U.S. patent did not issue until fifteen years later, on July 31, 1790), the U.S. Postal Service has received 660 patents since 1975, on things like digital stamps (US11348056) and mailboxes (D727589)

It’s hard to imagine the Postal Service ever enforcing these patents against FedEx or UPS, but they probably provide a good defense against third party claims against the Postal Service.