The length of time it takes to send a letter 20 miles depends on the time of year, location and type of postage used. However, most post offices can deliver a letter over this distance in one to two days.
When the post office picks up a letter, they do not take it directly to the address. Instead, the letter goes to the sorting facility, is given to the appropriate driver, and delivered as soon as possible. For letters, this process takes a day or two. Letters are marked with first class postage and given a higher priority during the sorting process than other types of mail.