What is oldest federal agency in the US?

The oldest federal agency in the United States is the United States Postal Service (USPS), which traces its origins back to 1775 when the Second Continental Congress established the position of Postmaster General. This agency has played a crucial role in the development of communication in the country. Although it was officially established as an independent agency in 1971, its roots in American history make it the oldest federal entity still in operation today.