Today we're going to discuss the history of the postal service. Before the 19th century, letters were usually delivered by private messengers, which was slow and costly. In 1840, Britain introduced the Penny Post, which allowed a letter to be sent anywhere in the country for just one penny. This was a revolutionary idea because it shifted the cost from the receiver to the sender. The system was so successful that other countries soon followed. However, it wasn't until the late 19th century that mail began to be sorted by machines, which greatly increased efficiency.