Pioneer Era (1893-1898)
Although there were earlier scattered issues, most pioneer cards in today's collections begin with the cards placed on sale at Chicago's Columbian Exposition in May of 1893. These were illustrations on government printed postal cards and privately printed souvenir cards. The government postal cards had the printed 1¢ stamp while the souvenir cards required a 2¢ adhesive postage stamp to be applied to it. Writing was not permitted on the address side of the cards.
Private Mailing Card Era (1889-1901)
On May 19, 1898, private printers were granted permission, by an act of Congress, to print and sell cards that bore the inscription "Private Mailing Card." Today some people call these cards PMCs. Postage required was a 2¢ adhesive stamp. A dozen or more American printers began to take postcards seriously. As with the Pioneer Era cards, writing was not permitted on the address side.
Post Card Era (1901-1907)
The use of the words "POST CARD" was granted to private printers by the U.S. government on December 24, 1901. Writing was still not permitted on the address side. In this era private citizens began to take black & white photographs and have them printed on paper with post card backs.
Divided Back Era (1907-1914)
Postcards with a divided back were permitted March 1, 1907. The address to be written on the right side and the left side was for writing messages. Many millions of cards were published in this era. Up to this point most postcards were printed in Germany, which was far ahead of the United States in the lithographic processes. With the advent of World War I the supply of postcards from Germany ended.
White Border Era (1915-1930)
Most postcards during this era were printed in the USA during this period. To save ink, a border was left around the view thus they are referred to as "White Border" cards. A high cost of labor, inexperience and public taste caused production of poor quality cards.
Linen Era (1930-1944)
New production processes allowed printing on post cards with high "rag" content that caused a "linen-like" finish. These inexpensive cards allowed the use of gaudy dyes for coloring. The firm of Curt Teich flourished on their line of linen postcards.
Photochrome Era (1945 to present date)
The "chrome" postcards started to dominate the scene soon after they were launched by the Union Oil Company in their western service stations in 1939.
Real photos are just that. A photograph was taken and developed. A caption was often hand-written on the negative, often glass. The photograph was printed on special postcard stock. Many real photos are one of a kind. Some were, relatively mass produced, usually by a photographer. Some clues are that if the caption is not neat, it probably was one of a kind. Mass produced cards usually were neater. Some of them carry the name of the photographer.