First U.S. Triangle Stamps
On March 13, 1997, the USPS issued its first triangle-shaped stamps to promote the upcoming Pacific ’97 Stamp Show.
The world’s first triangle-shaped stamps came 144 years earlier. Issued in 1853, the British colony Cape of Good Hope’s very first stamps were triangle-shaped. They were reportedly created in that shape to help illiterate postal clerks easily identify letters that were mailed from within the colony from those that were mailed from other places.