No founder, organization, proclamation, or campaign for the April 9 National Unicorn Day could be documented. The observance spreads through holiday-listing sites, museum and brand social posts, and the 2010s unicorn pop-culture wave, with no attestable origin event.
The horn that cost more than gold
Through the Middle Ages, European royalty paid fortunes for objects sold as unicorn horns. A single horn could be worth ten times its weight in gold. Buyers believed it could detect and neutralize poison, a serious concern for anyone with enemies and a dinner table.
The owners were not minor figures. Lorenzo de' Medici kept one. Pope Clement VII handed one to King Francis I of France. The horns were real objects, prized and guarded, and they were not from unicorns at all. In 1638 a Danish physician named Ole Worm showed what they actually were by displaying a narwhal skull with its long spiral tusk still attached.



