A Brief History of Postcards, Des Moines Library

Public Library in Des Moines, Iowa - postmarked in 1908 with one cent Franklin stamp
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Brief history of postcards in the United States

John P. Charlton of Philadelphia patented the postcard in 1861, selling the rights to H. L. Lipman, whose postcards, complete with a decorated border, were labeled "Lipman's postal card." Nine years later, European countries were also producing postcards.
Initially, the United States government prohibited private companies from calling their cards “postcards,” so they were known as “souvenir cards.” Although, in 1901, this prohibition was rescinded, not until 1908 could people write on the address side of a postcard.
The first postcard in the United States was created in 1893 to advertise the World's Columbian Exposition in Chicago. Shortly thereafter the United States government, via the United States Postal Service, allowed printers to publish a 1-cent postcard (the "Penny Postcard"). A correspondent's writing was allowed only on the front side of these cards.
Postcards, in the form of government postal cards and privately printed souvenir cards, became very popular as a result of the Columbian Exposition, held in Chicago in 1893, after postcards featuring buildings were distributed at the fair. In 1908, more than 677 million postcards were mailed.