1241 – After consolidating the invasion of the Kievan Russia to the east, the Mongols of Genghis Khan under the command of Subutai Bahadur, invade Poland, overwhelm Polish armies in Kraków and plunder the city.
1644 – The Third Anglo-Powhatan War begins in the Colony of Virginia.
1766 – After only being in effect in the American colonies for a few months, due to great protests, “No Taxation Without Representation”, the British Parliament repeals the Stamp Act. The protests by the colonists are generally considered to be the prelude of events that finally resulted in the Revolutionary War and American Independence.
1865 – At Washington City, Georgia, the Congress of the Confederate States adjourns for the last time and disbands.
1874 – King Kalākaua of Hawaii signs a treaty with the United States granting exclusive trade rights.
1937 – A natural gas leak explodes at the New London School in New London, Texas, killing 300 people, mostly children.
1959 – The Hawaii Admission Act is signed into law, with statehood for Hawaii coming into effect on August, 21.
1965 – Cosmonaut Alexei Leonov, leaving his spacecraft Voskhod 2, becomes the first person to walk in space.
1968 – The U.S. Congress repeals the requirement for a gold reserve to back US currency.
1990 – In the largest art theft in US history, 12 paintings, collectively worth around $500 million, are stolen from the Isabella Stewart Gardner Museum in Boston.