In 1873, the Postmaster General of the United States, John Creswell, issued the first pre-stamped 'penny postcard'. The postcard had been patented by John P. Charlton in 1861.
Richert, Lucas Paul. "First U.S. Postal Card issued". The Literary Encyclopedia. First published 20 December 2011
[http://www.litencyc.com/php/stopics.php?rec=true&UID=5974, accessed 23 September 2014.]