Postal cards are postal stationery with an imprinted stamp or indicium signifying the prepayment of postage. They are sold by postal authorities. On January 26, 1869, Dr. Emanuel Herrmann of Austria described the advantages of a Correspondenz Karte. By October 1, 1869 the world's first postal card was produced by Austria-Hungary. They caught on quickly. By the end of 1870, Great Britain, Finland, Switzerland and Württemberg joined the countries issuing postal cards. In the United States, they were first produced in 1873. Some of the forms taken by postal cards include the regular single card which may be commemorative or definitive, attached message-reply cards, airmail postal cards, and official postal cards used for official government business with a "penalty for private use".
To the post office, there were positive advantages to postal cards as opposed to correspondence in envelopes. The cards were lighter and less bulky than letters and they were all the same size. The result was that they occupied less than one third of the space required by the same number of letters. To the public there were also advantages. They were simple and cheap making them an instant success. Britain had a half-penny rate to begin with. The U.S. "penny postcard" rate lasted through 1951.