Original: Though postal services have existed on American territory before the United States' establishment, the USPS's first incarnation was established by Benjamin Franklin in Philadelphia in 1775 by decree of the Second Continental Congress.
Simplified: The United States Postal Service (USPS) was founded in 1775 and is located in Washington D.C./LOCATION. In the United States, it is referred to as "the post office", "the postal service", or just "the mail".