Do you know what a heliograph is and what it's most famous use was for? The heliograph was a mirror attached to surveying equipment that sent beams of light several miles using Morse code to alert the next station of upcoming newsworthy events. In the case of Arizona, the heliograph was used extensively to carry information distances of about 25 miles from fort to fort or station to station during the Apache wars. Hundreds of messages were sent between 23 heliographs, strategically positioned. The only time it actually intercepted Apache warriors was from Antelope Station.
Heliographs were quickly put into place after General Nelson A. Miles was sent to Arizona. Granted heliographs were a great communicator for the military Southwest, but their worth in closing the Apache War is widely contested. In fact, it is clearly debunked by the Official Fort Huachuca website.
it is also widely reported that the heliograph at the top of Mt. Graham was used in the war against Geronimo. This is incorrect. It was not introduced until 1889 when a wider network of heliographs were introduced. Within a few years though, heliograph communication was found to be largely ineffective and other forms of communication were developed.
Here is a great story of the Heliograph with pics from True West Magazine.