A USPS Mailbox is a drop-box for mail to be sorted, processed, and delivered by the United States Postal Service. The USPS dates back to 1775, when Benjamin Franklin became the first Postmaster General. Today, the USPS processes and delivers billions of pieces of mail every year, many of which are received through USPS Mailboxes. Blue USPS collection boxes can be used to mail any letter, or package weighing less than 13 ounces, that has a stamp.