Until 1847, local postmasters calculated the cost of postage, which varied depending on the number of sheets in the letter and its destination. The sender could pay all, part, of none of the postage. The addressee had to make up the difference.
In 1845, Congress lowered postal rates and made them more uniform. Two years later, Congress authorized the first postage stamp. Rates dropped again in 1851 -- down to 3 cents -- where they remained for more than 30 years.