U.S. Postal Service
According to the USPS website, "The Postal Service’s mission is to provide the nation with reliable, affordable, universal mail service. The basic functions of the Postal Service were established in 39 U.S.C. 101(a): '. . . to bind the Nation together through the personal, educational, literary, and business correspondence of the people. It shall provide prompt, reliable, and efficient services to patrons in all areas and shall render postal services to all communities.'"
So, we all use the post office. We all know what basic services it provides. That said, what isn't so apparent is that the Postal Service provides information and tools which may be useful to teachers.
Perhaps the most exciting possibilities can be found via the Postmaster Finder. How can you connect local history to national history? This may just be the answer. Try searching your town and state to find a list of area postmasters, dating back as early as 1639. This can give you insight into older names for your town, as well as providing leads to begin studying national communication by researching local postal history.
From there, you can compare period postal fleets to today's using postal service statistics. How has the nation grown from having one official postal station to over 32,000?
Finally, if you want to brush up on your postal history, the site offers a variety of relatively small sections on key dates; historical statistics; historical photographs; and postal service people, including past female and African American postmasters; and more.