Bare with me on all these post card images, but I'm still working with them and am fascinated by the different type treatments & the subtle variations in layouts. Why do they all say "Post Card"? And why is there a division line on some and not others?
After a little Wiki research, I discovered that post cards were originally only printed by the Post Office in the early 1890's. It was only after 1898 that private companies could start printing their own "post cards," and only after 1901 that they could call them "post cards," rather than "souvenir cards." And before 1907, you were only allowed to write on the front of the post card. After 1907, they created the "divided back" - one side for the address, one for correspondence. In 1908, more than 677 million post cards were mailed! This time was known as the Golden Age of Post Cards:) until 1915 when WWI prevented the import of German-printed post cards.