Potts

The first corner mailbox was patented in 1858. This design incorporated mailboxes onto lampposts. The boxes could be applied to existing lampposts, or new lampposts could be erected with the mailbox already built in. This was called the Potts mailbox. To view the patent, click here. Note that the Potts mailbox appears to wrap around the lamppost. A new, larger lamppost mailbox was issued in 1860. Therefore, it is unlikely that they appeared much later than 1860.

Potts Mailbox: Images courtesy of the Smithsonian National Postal Museum online exhibit