A while back I was looking at some of the oldest pictures ever taken. Most of these are cityscapes, and I found it fascinating the types and wording of the signs put on all the buildings. After all, aside from newspapers, if you wanted to address people, you made a big sign. Stuck on your house or establishment.
Are there any good or popular books about the history of signage? It was a such common form of public communication in times past, but I can't recall ever seeing anything about it.
That is an interesting question.
I'd suggest you poke around in histories of advertising. Best one I've read is Rick Fried's The Man Everybody Knew. It's a bio of Bruce Barton, more or less the root of modern American advertising.
Fried's book places Barton squarely at the center of creating modern American consumer, business, and political culture. It won't be directly on-point to your interest, but I'd bet there's something in the text or notes that would steer you in the right direction.