May 31

• May 31, 1223
  A coalition of several Rus' principalities is decisively defeated by the Mongol invaders under the command of generals Jebe and Subutai near the Kalka River in modern-day Ukraine
• May 31, 1433
  Sigismund is crowned Holy Roman Emperor of Rome
• May 31, 1469
  Manuel I of Portugal, king of Portugal, is born
• May 31, 1495
  Emperor Maximilian, Pope Alexander VI, Milan, King Ferdinand, Isabella and Venice sign anti-French Saint League
• May 31, 1564
  Lübeck and Denmark beat Sweden at Gotland during Northern Seven Years' War
• May 31, 1659
  Dutch Republic, England and France sign Treaty of The Hague during Second Northern War
• May 31, 1740
  Frederick William I of Prussia, king of Prussia, dies at age 51, and his son Frederick the Great comes to power in Prussia
• May 31, 1831
  Captain John Ross, an English explorer, identifies the magnetic north pole on the west coast of the Boothia Peninsula, Netsilik territory
• May 31, 1832
  Évariste Galois, a French mathematician and radical Republican, who developed a general theory of equations, dies from wounds suffered in a duel at age 20
• May 31, 1838
  The Federal Republic of Central America federation is dissolved as the congress meets to declare that the provinces were free to create their own independent republics
• May 31, 1859
  The tower clock known as Big Ben, located at the top of Elizabeth Tower at the north end of the Palace of Westminster, rings out over the Houses of Parliament in London for the first time
• May 31, 1862
  At the Battle of Seven Pines, McClellan defeat the Confederates outside of Richmond
• May 31, 1879
  First electric railway opens at Berlin Trades Exposition, Germany
• May 31, 1889
  Johnstown, Pennsylvania is destroyed by a massive flood after the South Fork Dam across a tributary of the Little Conemaugh River collapsed under pressure from the rain-swollen Lake Conemaugh killing 2,209 people in a flood and related fire
• May 31, 1889
  Johnstown, Pennsylvania is destroyed by a massive flood after the South Fork Dam across a tributary of the Little Conemaugh River collapsed under pressure from the rain-swollen Lake Conemaugh killing 2,209 people in a flood and related fire
• May 31, 1891
  Work on Trans-Siberian Railway, the longest railway line in the world, connecting Moscow with the Sea of Japan, begins
• May 31, 1902
  Second Boer War between the British Empire and the Afrikaans-speaking Dutch settlers, which has cost around 75,000 lives, ends leaving the Transvaal and the Orange Free State as colonies of the British Empire
• May 31, 1910
  The Union of South Africa is formed, incorporating Cape Colony, Natal, Orange Free State, and Transvaal
• May 31, 1915
  An LZ-38 Zeppelin makes first zeppelin air raid on London, England, killing 7 and injuring 35 people during the first bombing raid
• May 31, 1937
  German cruiser Deutschland bomb Almería, Spain during Spanish Civil War
• May 31, 1943
  Japanese forces are driven from Aleutian Islands, Alaska
• May 31, 1961
  South Africa becomes a republic following a referendum in which white voters narrowly voted in favour thereof
• May 31, 1970
  A kilometer wide avalanche mass of ice, mud and rock, triggered by an earthquake in Peru, advances about 18 km and leads to more than 20,000 death
• May 31, 1988
  U.S. President Ronald Reagan addresses 600 Moscow State University students, during his visit to the Soviet Union
• May 31, 1997
  Official opening of the Confederation Bridge, between Prince Edward Island and New Brunswick, Canada, the world's longest bridge spanning ice covered waters