Envelopes were not commonly used in the United States before 1850.
Before postal reform in the mid-19th century, postage in the United States was expensive and based on the amount of paper being mailed. For this reason, letters were typically written as a self-contained folio, which was folded for mailing.
An example of letter folding can be seen in the letter sent to Colonel Hook by Dr. Buck, who examined him after his duel. You can see the lines where this letter was originally folded for mailing.
First, Dr. Buck folded the letter in half vertically to create a folio. Then he folded it into an envelope. In the picture, you can see five vertical folds and two horizontal folds. The video below shows how Dr. Buck would have folded his letter.
What would you want to write to Colonel Hook, a career soldier born soon after the Revolutionary War? Follow along to better understand the folding process, see its effect on paper, and create your own folio letter.
This letter is currently on display at the Hook Exhibit.
Colonel Hook Papers 