The first transcontinental telegraph message was sent in 1861, bringing to an end the Pony Express

The Pony Express was a fast mail service crossing the Great Plains and the Rocky Mountains from St. Joseph, Missouri, to Sacramento, California, from April 1860 to October 1861. It became the west's most direct means of east-west communication before the telegraph and was vital for tying California closely with the Union just before the American Civil War.

This original fast mail Pony Express service had messages carried by horseback riders in relays to stations across the prairies, plains, deserts, and mountains of the Western United States. For its 18 months of operation, it briefly reduced the time for messages to travel between the Atlantic and Pacific coasts to about ten days, with telegraphic communication covering about half the distance across the continent and mounted couriers the rest.

- Wikipedia

Science Fair Project Information
Title: Build Your Own Morse Telegraph System
Subject: Electromagnetism
Grade level: Middle School, Grades 7-9
Academic Level: Ordinary
Project Type: Building project
Cost: Low
Affiliation: Science Fair Projects and Experiments
Description: A very basic and simple apparatus consisting of a morse key, battery, bulb or LED, buzzer and an electromagnet.
Link: http://www.juliantrubin.com/bigten/morsetelegraph.html