The Tripolitan War, between the United States and the Barbary States, began.
Wagner's opera, Tristan and Isolde, premiered in Munich.
Alcoholics Anonymous was founded by "Bill W."
The entire male population of the Czech village of Lidice was massacred in retaliation for the death of Nazi official Reinhard Heydrich.
Italy replaced its monarchy with a republic.
The Six-Day War between Israel and Syria, Egypt, and Jordan ended.
Affirmed won the Belmont Stakes and the Triple Crown.
Ontario, Canada issued the first full same-sex marriage licenses in North America.