TDAXP has sent me an interesting article on optical telegraphs (semaphore). The semaphore was a device which allowed messages to be sent by flag combinations.
The original idea for the semaphore was thought up in the 1600s but it was not until the late 1700s when a system was actually put into place. France was the first country to use the tool and used it for republican communications during the revolution. The first message was a coded one between Paris and Lille.
Other countries used the system as well including Sweden (who independently invented their own system), the British (who used their system for naval/coastal communications), Prussia, Russia, and the United States.
Geography proved to be the systems done fall, though. While ports in the United States used flag communications, the sheer size and variety of terrain obsticals made the optical telegraph inefficent for long distance communication. The need for a better system led to the creation of the electric telegraph we all know of.
For some maps and more information (in French) on the optical telgraph click here.