[rmacpa]

the following was excerpted from a website devoted to the history of united states postcards.

"Modern Postcard Era - Divided Back Postcards (1907 - Present)

The final major change in postcard design came with the new postcard regulations of March 1, 1907, which allowed the back of postcards to be divided down the center. The right side of the back was now for the address and postage and the left side was for the personal message that used to be written on the front of the card.

Because this is essentially the same basic design that is still in use today for postcards, March 1, 1907 is considered the birthday of the modern postcard. However, printers wanting to save money continued using their old designs for a time. So it is common to see postcards that were made after 1907 that still have some white space on the front for writing or to see the undivided backs with a line simply drawn down the middle."