- 1525 The Swiss Anabaptist Movement is born when Conrad Grebel, Felix Manz, George Blaurock, and a dozen others baptize each other in the home of Manz's mother in Zürich, breaking a thousand-year tradition of church-state union
- 1793 Louis XVI of France is executed by the guillotine in Paris, following his conviction for high treason
- 1968 The Battle of Khe Sanh - one of the most publicized and controversial battles of the Vietnam War - begins at the Khe Sanh Air Base
- 2008 Black Monday in worldwide stock markets. FTSE 100 had its biggest ever one-day points fall, European stocks closed with their worst result since 9/11, and Asian stocks drop as much as 15%.
1st American novel, WH Brown's "Power of Sympathy" is published
On January 21, 1789
New York City regulation makes it illegal for a woman to smoke in public
On January 21, 1908