U.S. Special Delivery was a postal service paid for with additional postage for urgent letters and postal packets which are delivered in less time than by standard or first class mail service. Its meaning is different and separate from express mail delivery service. Essentially it meant that a postal packet was delivered from a post office to the addressee immediately once it arrived at the post office responsible for delivering it, rather than waiting for the next regular delivery to the addressee.

The United States Postal Service (USPS), also known as the Post Office, U.S. Mail, or 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 its associated states. It is one of the 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.