United States Postal Service
The United States Postal Service (USPS), also known as the Post Office, U.S. Mail, or simply the Postal Service, is an independent agency of the executive branch of the United States federal government responsible for providing postal service in the United States, its insular areas and associated states. It is one of a few government agencies explicitly authorized by the Constitution of the United States. As of 2023, the USPS has 525,469 career employees and 114,623 non-career employees. : 3 
The USPS has a monopoly on traditional letter delivery within the U.S. and operates under a universal service obligation (USO), 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. The Post Office has exclusive access to letter boxes marked "U.S. Mail" and personal letterboxes in the U.S., but has to compete against private package delivery services, such as United Parcel Service, FedEx, and DHL.