Each stamp printed for postal service is first placed on sale in the post office of whatever city is pertinent to the issue. If it commemorates a famous person, as an example, the first day of issue would more than likely be the city in which that person was born. If the stamp is in commemoration of some historical or national event or landmark, the first day issue location would be the city nearest the place where the event occurred or the landmark was located.

While the new issue of stamps is sent to post offices all over the country, the postmasters are instructed to withhold the sale of them until the day after the day of issue. This means that if the first day sale is on the first of the month, local post offices in other than the first day city cannot sell the stamps until the second of that month.

First day covers have become a big thing in stamp collecting, and several companies are now engaged in printing very elaborate envelopes for sale as first day covers.