Quick Answer: The United States 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. The USPS began operations in 1971, replacing the United States Post Office Department, a Cabinet department. As of March 29, 2024, the USPS has 525,377 career employees and nearly 114,623 pre-career employees. The USPS has a monopoly on traditional 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.