People began collecting postage stamps almost immediately after the first example, the Penny Black, was issued in 1840. Today it is one of the world's most widely enjoyed hobbies, and it is estimated that there are 20 million stamp collectors just in the United States.
While many people collect stamps as nothing more than a recreational activity, some stamps have become highly valuable objects. Perhaps the most famous example in American history is the Inverted Jenny stamp. The origin of the Inverted Jenny goes back to 1918, when the USPS initiated trails in airmail service. Airmail cost 24 cents at the time, three times the rate for regular mail, and the Postal Service printed special stamps for the new class of mail. These stamps featured the image of a Curtiss JN-4 “Jenny” biplane, the type of plane that was used in the early air-mail experiment, in blue ink, with a border of red containing the words “U.S. Postage, 24 cents.
This two-color process required the sheets of stamps to be run through printing presses twice, and at least four sheets (of 100 stamps each) of these early airmail stamps was printed with an error: the Jenny biplane was upside down. Three of them were caught and destroyed before they left the production facility, but one sheet slipped through into circulation. Mistakes such as this had occurred before with other stamps, which had then become collectible, so stamp collectors were seeking out the Inverted Jennies shortly after they were printed.
One such collector was lucky enough to have bought that sheet of Inverted Jennies at his local post office. He then sold it to a stamp dealer for $15,000, quite the sum in 1918. Since then, the sheet was broken up, mostly into blocks of four and several individuals. One block of four Inverted Jennies recently sold for nearly $3 million.
The Inverted Jennies' fame has only grown, partly through the influence of popular culture. They have featured in the story lines of mystery novels, film comedies, and even an episode of The Simpsons, a show honored with its own USPS stamps last year. There's no word on any Inverted Homers. At least, not yet.