There were optical telegraphs before electrical: https://en.m.wikipedia.org/wiki/Optical_telegraph

"The Early History of Data Networks" is a good read on the topic: https://books.google.com/books/about/The_Early_History_of_Da...

That's a mind blower, I did not know about it thank you.

The coding for the optical telegraphs seemed primitive to me. I wonder if you couldn't come up with a system that mixed signals going both ways.

The semaphore tower method could maybe have supported mixed signals with one operator dedicated to receive/forward and the other operator dedicated to acknowledge with a detailed response.

A series of "glyphs" that mixed forward signals and backward signals would help. Old school "local loop" telephones electrically multiplexed signals, but the optical telegraphs were quite a bit more discrete.

I saw a picture of a stretch of road in the west and started thinking about the 1800's and the striking contrast between the wild and the technological American landscape. It turns out Google has an interesting site, linked.