What revolutionized American communications in the late 1800's?

Well, the type writer and the telephone would be the first things that come to mind.

The incandescent light bulb is another one. - I think this would only qualify as an revolution to the communications of America if you factored in it being used as a light signal on boats, and even that is arguable. While it is a major invention, I don't see it as a communication revolution.