The Pony Express (1860-1861) was short lived and soon to be replaced by telegraph wires. It represented an early - and important - attempt to bind the far-reaches of the nation. At a time when the nation was threatening to break apart at the seams with the Southern Rebellion, it was important that the Far West recognize that it was a part of the Union. An expensive letter carried by Pony Express riders wasn't a great solution, but it was the best one for those few months before the telegraph could deliver news and messages from coast to coast. Before that, Californians had to wait for the latest ship to arrive with letters delivered by ship to Central America, across the isthmus, and then to ship again to the North American Pacific coast. The Pony Express represented an early effort to solve that problem, and lacking a better option (until telegraph wires linked the coasts), it was something to be grateful for.

edited to make it clear how the nation was tearing itself apart - "with the Southern Rebellion".