Interesting random article from the StackExchange network. How do you perform long distance communication before electricity? Lighthouses are one method, but when you mention this, sound was another great way of communication in ye olden days before cars, trains, factories, and whatnot noised up the air and made in impractical to use sound to communicate for more than a mile’s distance. Oh, how I long for a world where there was not so much noise pollution from industrial machinery and over-amplified sound.
20190926/https://worldbuilding.stackexchange.com/questions/156969/lighthouse-alternatives