Dear Matthew Barrett,
As it happens, postage stamps have only been used since 1840... And only because people were trying to cheat the post office...because traditionally the person receiving the letter had to pay the delivery charges.
Well, the senders began putting secret marks on the outside of the letter, so the recipient could then refuse delivery and see the message for free!
So Sir Rowland Hill, the British Postmaster General at the time, introduced the idea of the SENDER paying the fee and affixing a little piece of colored paper as a receipt...and that is how things have gone now since May 6, 1840.
And here you are, this is the very first postage stamp, honoring Queen Victoria...printed in black, came to be known as the "penny black."
From the website of the American Philatelic Society, http://stamps.org/Stamp-History
