The envelope was sent twice: once on May 2, 1840, and again on May 4, 1840. Sotheby's The first known piece of mail sent with a prepaid, adhesive stamp could sell for as much as $2.5 million.

A postage stamp is a small but mighty canvas, sealing history onto every envelope with a historic image, vibrant ink and adhesive. When these miniature tributes bring to our everyday lives the leaders ...