July 1, 1847 — The first US postage stamps went on sale in New York today. The 5-cent stamp featured Benjamin Franklin; George Washington starred on the 10-cent stamp.

Previously, letters were paid for by the receiver unless already prepaid by the sender. As you can imagine, this system was chaotic and hard to enforce, for the receiver could send the mail back to the post office without paying for it. Once stamps were issued, payments were regulated and the mail moved much more efficiently. By 1855, stamps became mandatory.

Sources: postalmuseum, wikipedia