Site oficial: http://www.usps.com/
The United States Postal Service (originally called the U.S. Post Office Department, when it was completely managed by the U.S. Government before 1971) also known as the Post Office, U.S. Mail, or Postal Service is an independent agency of the United States federal government responsible for providing postal service in the United States. It is one of the few government agencies explicitly authorized by the United States Constitution. The USPS traces its roots to 1775 during the Second Continental Congress, where Benjamin Franklin was appointed the first postmaster general. The cabinet-level Post Office Department was created in 1792 from Franklin's operation and transformed into its current form in 1971 under the Postal Reorganization Act. The USPS employed 626,764 workers (as of January 2014) and operated 211,654 vehicles in 2013. The USPS is the operator of the largest civilian vehicle fleet in the world. The USPS is legally obligated to serve all Americans, regardless of geography, at uniform price and quality. The USPS has exclusive access to letter boxes marked 'U.S. Mail' and personal letterboxes in the United States.