Doctor Dolittle's Post Office by Hugh Lofting

Now, this Fantippo post office of which Zuzana had spoken to the Doctor was rather peculiar. For one thing, it was, of course, quite unusual to find a post office or regular mails of any kind in a savage African kingdom. And the way such a thing had come about was this:

A few years before this voyage of the Doctor's there had been a great deal of talk in most civilized parts of the world about mails and how much it should cost for a letter to go from one country to another. And in England a man called Rowland Hill had started what was called "The Penny Postage," and it had been agreed that a penny a letter should be the regular rate charge for mails from one part of the British Isles to another. Of course, for specially heavy letters you had to pay more. Then stamps were made, penny stamps, twopenny stamps, twopence-halfpenny stamps, sixpenny stamps and shilling stamps. And each was a different color and they were beautifully engraved and most of them had a picture of the Queen on them -- some with her crown on her head and some without.