The Transcontinental Telegraph was a communication system that connected the eastern and western United States in the 1860s. Completed in 1861, it allowed messages to be sent quickly across the country, significantly reducing the time it took to communicate compared to previous methods like the pony express. This telegraph line used a series of wires and relay stations, enabling messages to travel from Washington, D.C. to San Francisco in just a matter of hours. The project was crucial for the expansion of the United States, facilitating commerce, news dissemination, and the coordination of activities during the Civil War.