June 20

• June 20, 451
  Combined Roman and Visigoth forces under Roman general Flavius Aetius stop Attila's army at the Catalaunian Plains in eastern France, the last great military campaign by Western Roman Empire
• June 20, 656
  Caliph Uthman ibn Affan is assassinated, thus Ali becomes caliph
• June 20, 840
  King of the Franks Louis the Pious dies triggering the Civil war in Frankish kingdom between his sons
• June 20, 1646
  In England, Parliament signs a peace treaty with Royalists
• June 20, 1675
  A band of Pokanoket retaliate for the execution of three of their people and attack several isolated homesteads in the small Plymouth colony settlement of Swansea, starting King Philip's War
• June 20, 1743
  The British warship Centurion under Commodore George Anson engaged and overcame the Spanish treasure galleon, Nuestra Senora de Covadonga, near the Philippines killing 58 Spaniards and capturing over 1 million Spanish silver dollars and 500 pounds of native silver
• June 20, 1756
  In India rebels defeat the British army at Calcutta and imprison between 64 and 146 British soldiers in a suffocating cell that gained notoriety as the Black Hole of Calcutta
• June 20, 1789
  Oath on the Tennis Court in Versailles, France, bonds members of the Third Estate to resist eviction until they have a new constitution
• June 20, 1791
  King Louis XVI is caught trying to escape French Revolution in the so-called Flight to Varennes
• June 20, 1793
  Eli Whitney, an American inventor, petitions patent for a cotton gin, a machine which cleans the tight-clinging seeds from short-staple cotton, which becomes one of the key inventions of the Industrial Revolution
• June 20, 1819
  The paddle-wheel steamship Savannah arrives in Liverpool, England, after a voyage of 27 days and 11 hours and becomes the first steamship to successfully cross the Atlantic
• June 20, 1837
  Queen Victoria ascends the British throne following the death of her uncle, King William IV, and beginning the Victorian era when the British Empire get the apex
• June 20, 1877
  Alexander Graham Bell installs the world's first commercial telephone service in Hamilton, Ontario, Canada
• June 20, 1893
  A jury in New Bedford, Massachusetts, finds Lizzie Borden innocent of the ax murders of her father, wealthy Fall River, Massachusetts, businessman Andrew Borden and his wife, Abby Borden, however, is ostracized for the rest of her life
• June 20, 1948
  West German Finance Minister Ludwig Erhard eliminates most price controls and introduces a new currency, the "Deutsche mark"
• June 20, 1960
  Federation of Mali, with Senegal, becomes independent of France
• June 20, 1990
  The asteroid Eureka, the first Mars trojan, is discovered by David H. Levy
• June 20, 1991
  The Bundestag in Bonn decides that Berlin should become the German capital
• June 20, 2003
  The North East MRT Line, the world's first fully automated and driverless subway opens in Singapore