The United States Postal Service (USPS) is an independent agency of the executive branch of the United States federal government responsible for providing postal service in the United States. It is one of the few government agencies explicitly authorized by the United States Constitution.
The USPS has a monopoly on "letter" delivery within the United States and operates under a universal service obligation, both of which are defined across a broad set of legal mandates, which obligate it to provide uniform price and quality across the entirety of its service area. USPS has exclusive access to letter boxes marked "U.S. Mail" and personal letterboxes in the United States, but has to compete against private package delivery services, such as United Parcel Service, FedEx, and Amazon.
