24-cents turned into $1-million . . .
when the Post Office made a mistake printing the nation's "first air mail stamp." It all happened in 1918, when the U.S. inaugurated regular air mail service between Washington D.C., Philadelphia and New York City . . . aboard the Curtiss JN-4 "Jenny" biplane. Printing of the new 24-cent air mail stamps was done in 2 colors (red and blue), and required that sheets of 100 stamps be fed through the printing press twice (once for each color) . . . an error-prone process which caused some sheets to be printed with an "inverted" Jenny biplane. (Oops!) It is believed only one misprinted sheet got through unnoticed . . . and thus the birth of the rarest of all U.S. stamp errors (and most valuable) . . .
The 24-cent Inverted Jenny
One perfect, mint condition "inverted Jenny" stamp sold at auction in 2007 for $978,000 . . . and is estimated to be worth well in excess of $1-million today. (Pretty good return for a 24-cent purchase at the Post Office!)
And believe it or not, when the Postal Service started selling stamps and delivering our mail (1850s), all you needed to address was the person's name, plus a city and state. (Imagine addressing a letter . . . Lafayette Whithed Esq, St. Louis, Missouri. And your letter would arrive!)
As city populations grew, the addition of a street and number would be required (by the turn of the century.) In 1943, city "2 digit" postal codes were required (e.g. St. Louis 08, Missouri). And in 1963, the 5-digit Zip Code was introduced (e.g. St. Louis, MO 63108). Zip Codes grew once again in 1983 with the "Zip + 4" codes (e.g. 63108-2336) which designated individual carriers to deliver our mail.
Getting complicated, isn't it?