I wonder why it was written sideways.
I have a few like that too. If I had to guess, I'd say it was the newness of post cards and people didn't have a traditional way of doing it.
Postcards in the US were first allowed by Congress to be sent though the mail in 1898. According to Wiki, postcards were allowed to have a divided back starting March 1907 - and prior to that messages were written on the front.
I have some of the older ones with space on the front specifically for writing , and some where the writing is crowded around the edges of the image - and a few where the sender simply wrote over the image. Let me find some good examples to post
