Historic Postcards of the Slate Belt

The Post Office was the only establishment allowed to print postcards, and it held its monopoly until May 19, 1898, when Congress passed the Private Mailing Card Act, which allowed private publishers and printers to produce postcards. The slate industry took advantage of the new promotional medium with a wide range of images used as postcards, although Images of large scale industrial sites and applications, which would seem odd in the current market, were very common at the time, reflecting United States pride in its manufacturing and industry. Many of these images were used over and over by different companies, and some of them are clearly from images taken by members of the Pennsylvania Geological Survey. As the techniques of making postcards and the rules for using them changed, so did the quality of the images, including the addition of color through a painted process. The so-called golden age of hand-coloured photography in the western hemisphere occurred between 1900 and 1940. Originally postcards were not allowed to have a divided back and correspondents could only write on the front of the postcard. This was known as the "undivided back" era of postcards. Starting March 1, 1907 the Post Office allowed private citizens to write on the address side of a postcard. It was on this date that postcards were allowed to have a "divided back". (SOURCE)