May 1

• May 1, 305
  Constantius Chlorus and Galerius become Western and Eastern emperors, after Diocletian leaves the imperial office due to illness becoming the only Roman emperor to voluntarily abdicate the position
• May 1, 408
  Theodosius II succeeded to the throne of Constantinople
• May 1, 1486
  Christopher Columbus convinces Queen Isabella to fund expedition to the West Indies
• May 1, 1648
  The Ottomans begin the Siege of Candia in order to capture Crete from the Venetians
• May 1, 1707
  Act of Union merging the Scottish and the English Parliaments takes effect, thus establishing the Kingdom of Great Britain
• May 1, 1711
  Arch duke Charles VI of Austria and Hungarian rebellion sign Treaty of Szatmár
• May 1, 1759
  France surrenders Guadeloupe to Great Britain
• May 1, 1776
  Adam Weishaupt, a German philosopher, founds the secret society of Illuminati to oppose superstition, religious influence over public life, abuses of state power, and to support gender equality
• May 1, 1786
  Opera "Marriage of Figaro", composed by Wolfgang Amadeus Mozart, an Austrian influential composer of the Classical era, is premiered in Vienna
• May 1, 1840
  Britain issues the world's first postage stamp, "Penny Blacks", depicting a picture of Queen Victoria, as prepaid postage innovation
• May 1, 1851
  The Great Exhibition in London, the world's first international Expo, is opened in Crystal Palace, a cast-iron and plate-glass building erected in Hyde Park, as a showcase for industrial accomplishments of Great Britain and other countries
• May 1, 1853
  Argentina adopts its liberal and federal Constitution constitution
• May 1, 1857
  William Walker, conqueror of Nicaragua, surrenders to the US Navy under the pressure of the Central American armies
• May 1, 1862
  USA Army captain David Farragut recaptures New Orleans, Louisiana which stops cotton sales by the Confederacy a revenue shortage that led to printed money and hyperinflation
• May 1, 1869
  Folies Bergère, a cabaret music hall, opens in Paris
• May 1, 1873
  Emperor Franz Jozef opens 5th World's Fair in Vienna, Austria-Hungary
• May 1, 1876
  Queen of the United Kingdom Victoria takes title of Empress of India by Royal Titles Act
• May 1, 1877
  US President Rutherford B. Hayes orders the withdrawal all Federal troops from the South, ending Reconstruction
• May 1, 1884
  Construction begins on the first steel-skeleton skyscraper, a 10-story structure in Chicago, designed by William Le Baron Jenney and built by the Home Insurance Co. of New York
• May 1, 1889
  Bayer, a German chemical and pharmaceutical company, introduces aspirin in powder form
• May 1, 1896
  Naser al-Din Shah Qajar, shah of Persia, is murdered by Mirza Reza Kermani, a follower of Jamal al-Din al-Afghani, at age 65
• May 1, 1898
  The American Asiatic Squadron under George Dewey destroy the Spanish Pacific Squadro during the Battle of Manila Bay
• May 1, 1924
  Admiral Pavlos Kountouriotis becomes the first President of Greece
• May 1, 1925
  Cyprus is declared a British Crown Colony
• May 1, 1930
  The dwarf planet Pluto is officially named
• May 1, 1931
  Empire State Building is officially opened, when United States President Herbert Hoover turns on the building's lights with the push of a button from Washington, D.C
• May 1, 1932
  Paul Doumer, President of France, is assassinated by mentally unstable Russia's Paul Gargalov
• May 1, 1947
  The U.S. Central Intelligence Agency is created
• May 1, 1956
  A doctor in Japan reports an "epidemic of an unknown disease of the central nervous system," marking the official discovery of Minamata disease
• May 1, 1960
  Russia shoots down American pilot Francis Gary Powers' U-2 spy plane over Sverdlovsk
• May 1, 1964
  At Dartmouth College, in Hanover, New Hampshire, the BASIC programming language runs for the first time, developed by professors John Kemeny and Thomas Kurtz for a General Electric 225 mainframe computer
• May 1, 1978
  Japan's Naomi Uemura, traveling by dog sled, becomes the first person to reach the North Pole alone
• May 1, 2006
  Bolivian president Evo Morales orders military to occupy oil and gas fields in country, placing them under state control
• May 1, 2011
  U.S. President Barack Obama announces that Osama bin Laden, the founder and leader of the militant group Al-Qaeda, has been killed during an American military operation in Pakistan