July 21 events in history

230 Pope Pontian succeeds Urban I as the eighteenth pope
285 Diocletian appoints Maximian as Caesar and co-ruler
365 A tsunami devastates the city of Alexandria, Egypt. The tsunami was caused by the Crete earthquake estimated to be 8.0 on the Richter scale. Five thousand people perished in Alexandria, and 45,000 more died outside the city
1242 Battle of Taillebourg : Louis IX of France puts an end to the revolt of his vassals Henry III of England and Hugh X of Lusignan
1403 Battle of Shrewsbury: King Henry IV of England defeats rebels to the north of the county town of Shropshire, England
1545 The first landing of French troops on the coast of the Isle of Wight during the French invasion of the Isle of Wight
1568 Eighty Years' War: Battle of Jemmingen – Fernando Álvarez de Toledo, Duke of Alva defeats Louis of Nassau
1645 Qing Dynasty regent Dorgon issues an edict ordering all Han Chinese men to shave their forehead and braid the rest of their hair into a queue identical to those of the Manchus
1656 The Raid on Malaga takes place during the Anglo-Spanish War
1718 The Treaty of Passarowitz between the Ottoman Empire, Austria and the Republic of Venice is signed
1774 Russo-Turkish War (1768–1774): Russia and the Ottoman Empire sign the Treaty of Küçük Kaynarca ending the war
1831 Inauguration of Leopold I of Belgium, first king of the Belgians
1861 American Civil War: First Battle of Bull Run – at Manassas Junction, Virginia, the first major battle of the war begins and ends in a victory for the Confederate army
1865 In the market square of Springfield, Missouri, Wild Bill Hickok shoots and kills Davis Tutt in what is regarded as the first western showdown
1873 At Adair, Iowa, Jesse James and the James-Younger Gang pull off the first successful train robbery in the American Old West
1877 After rioting by Baltimore and Ohio Railroad workers and the deaths of nine rail workers at the hands of the Maryland militia, workers in Pittsburgh, Pennsylvania stage a sympathy strike that is met with an assault by the state militia
1902 Willis Carrier creates the first air conditioner in Buffalo, New York
1903 Battle of Ciudad Bolívar, a victory of federal army of Juan Vicente Gómez over forces of general Nicolás Rolando
1904 Louis Rigolly, a Frenchman, becomes the first man to break the 100 mph (161 km/h) barrier on land. He drove a 15-liter Gobron-Brille in Ostend, Belgium
1907 The passenger steamer SS Columbia collides with the steam schooner San Pedro off Shelter Cove, California, causing the Columbia to sink killing 88 people
1914 The Crown council of Romania decides for the country to remain neutral in World War I
1918 U-156 shells Nauset Beach, in Orleans, Massachusetts
1919 The dirigible Wingfoot Air Express crashes into the Illinois Trust and Savings Building in Chicago, Illinois, killing 12 people
1925 Sir Malcolm Campbell, father of Donald Campbell, becomes the first man to break the 150 mph (241 km/h) land barrier at Pendine Sands in Wales. He drove a Sunbeam at a two-way average speed of 150.33 mph (242 km/h)
1925 Scopes Trial: In Dayton, Tennessee, high school biology teacher John T. Scopes is found guilty of teaching evolution in class and fined $100
1944 World War II: Battle of Guam – American troops land on Guam starting the battle. It would end on August 10
1944 World War II: Claus von Stauffenberg and fellow conspirators are executed in Berlin, Germany for the July 20 plot to assassinate Adolf Hitler
1949 The United States Senate ratifies the North Atlantic Treaty
1954 First Indochina War: The Geneva Conference partitions Vietnam into North Vietnam and South Vietnam
1959 NS Savannah, the first nuclear-powered cargo-passenger ship, is launched as a showcase for Dwight D. Eisenhower's "Atoms for Peace" initiative
1959 Elijah Jerry "Pumpsie" Green becomes the first African-American to play for the Boston Red Sox, the last team to integrate. He came in as a pinch runner for Vic Wertz and stayed in as shortstop in a 2–1 loss to the Chicago White Sox
1961 Mercury program: Mercury-Redstone 4 Mission – Gus Grissom piloting Liberty Bell 7 becomes the second American to go into space (in a suborbital mission)
1970 After 11 years of construction, the Aswan High Dam in Egypt is completed
1972 The Troubles: Bloody Friday – the Provisional IRA detonate 22 bombs in central Belfast, Northern Ireland, United Kingdom in the space of 80 minutes, killing nine and injuring 130
1973 In the Lillehammer affair in Norway, Israeli Mossad agents kill a waiter whom they mistakenly thought was involved in the 1972 Munich Olympics Massacre
1976 Christopher Ewart-Biggs, the British ambassador to the Republic of Ireland, is assassinated by the Provisional IRA
1977 The start of the four day long Libyan–Egyptian War
1983 The world's lowest temperature in an inhabited location is recorded at Vostok Station, Antarctica at −89.2 °C (−128.6 °F)
1995 Third Taiwan Strait Crisis: The People's Liberation Army begins firing missiles into the waters north of Taiwan
2011 NASA's Space Shuttle program ends with the landing of Space Shuttle Atlantis on mission STS-135
2012 Erden Eruç completes the first solo human-powered circumnavigation of the world