The 19th century proved to be a transformative century in communications and transportation. The mission of the Post Office Department to provide universal service was constantly challenged by growing territory and an increasing number of immigrants settling in the cities and migrating to new territories. New technology was being used in new and innovative ways. Most notably, the railroad and the stamp.
The first railroad was used to carry the mail in the 1830s and as tracks were laid and standardized, the government designated the routes as postal roads. Similar policies on rivers and canals gave the mail a vast network east of the Mississippi. But the mail would travel from town to town in an enclosed bag meaning that only after it reached its destination could it be sorted and sent along on the next train for mail moving to the next town. Increasing demands for efficiency, brought on by the restricting resources of the Civil War inspired a postmaster in Illinois to have his clerks open the bags while on the train and sort them so that at each stop, only the mail designated for that town would be dropped off. This transformed into the most efficient system used for mail processing and delivery well into the 20th century.
Before 1847, if you wanted to send a letter, you would address it and drop it off to be delivered. Payment was required, but it would be demanded from the recipient. Sometimes that person wouldn’t or couldn’t pay. Or they could not be found and the post office would have done all the work to deliver the letter without getting any money for the service. This brought the cost up for everyone sending a letter.
After the adoption of the use of stamps, which showed pre-payment, more letters could arrive at their final destination for a fraction of the price. The cost of mailing a letter dropped and became reasonable for more people to use the service.