These sites are about the U.S. postal services. Learn what they do, about the mail delivery process, technologies used, how a postal system works, and how countries collaborate to deliver mail. Includes the history of the U.S. postal service, types of mail, key people, and the zip code system. There are also video clips, lesson plans, and teaching resources. Includes links to eThemes Resources on the Pony Express and Postage Stamps.