National Postal Museum

National Postal Museum is at 2 Massachusetts Ave. N.E. Ever wondered why Zoning Improvement Plan (ZIP) codes came into being, how letter tracking works or what a Carrier Sequence Bar Code Sorter is? You'll find out here. This Smithsonian museum is housed in the Old City Post Office, built in 1914. Permanent exhibitions explore the history of U.S. mail service. Binding the Nation takes a look at the beginnings of establishing postal service between New York and Boston in the 1670s—an era when envelopes, postage stamps and mailboxes didn't exist and paper had to be imported. Behind the Badge spotlights the work of the U.S. Postal Inspection Service and its efforts to keep the mail safe from an array of frauds and scams. At the entrance is a mobile command center vehicle, a high-tech unit complete with power supplies and forensics lab materials. Stamp collectors should not miss the William H. Gross Stamp Gallery on the lobby level, which offers a fascinating look at postage stamp history. Visitors will learn about the Penny Black, the world's first postage stamp, issued in Great Britain on May 1, 1840, and the Inverted Jenny, with its upside-down blue plane that is one of history's most famous printing errors. The world's rarest and most valuable stamp, the 1856 British Guiana One-Cent Magenta, is on display in the gallery's World of Stamps exhibition. A periodically rotating selection of stamps, housed in pullout wall frames, spotlights examples from the museum's massive collection (including stamps from countries that no longer exist). Here you'll see an Elvis Presley stamp, issued Jan. 8, 1993, that is the top-selling stamp in U.S. history (nearly 520 million and counting). Budding collectors can search through boxes of stamps from around the world and take home six to start their own collection. Adjacent to the gallery is the Postmasters Gallery, which features rotating exhibits. This suite of rooms with walnut-paneled walls and wood parquet floors was once the office of the D.C. city postmaster. Guided tours are available. Time: Allow 1 hour minimum.