1256 – The Augustinian monastic order is constituted at the Lecceto Monastery when Pope Alexander IV issues a papal bull Licet ecclesiae catholicae.
1415 – Religious reformers John Wycliffe and Jan Hus are condemned as heretics at the Council of Constance.
1436 – Assassination of the Swedish rebel (later national hero) Engelbrekt Engelbrektsson
1471 – Wars of the Roses: The Battle of Tewkesbury: Edward IV defeats a Lancastrian Army and kills Edward of Westminster, Prince of Wales.
1493 – Pope Alexander VI divides the New World between Spain and Portugal along the Line of Demarcation.
1626 – Dutch explorer Peter Minuit arrives in New Netherland (present day Manhattan Island) aboard the See Meeuw.
1686 – The Municipality of Ilagan is founded in the Philippines.
1776 – Rhode Island becomes the first American colony to renounce allegiance to King George III.
1799 – Fourth Anglo-Mysore War: The Battle of Seringapatam: The siege of Seringapatam ends when the city is invaded and Tipu Sultan killed by the besieging British army, under the command of General George Harris.
1814 – Emperor Napoleon I of France arrives at Portoferraio on the island of Elba to begin his exile.
1814 – King Ferdinand VII of Spain signs the Decree of the 4th of May, returning Spain to absolutism.
1836 – Formation of Ancient Order of Hibernians
1859 – The Cornwall Railway opens across the Royal Albert Bridge linking Devon and Cornwall in England.
1865 – Surrender of the Confederate departments of Alabama, Mississippi and East Louisiana at Citronelle, Alabama.
1869 – The Naval Battle of Hakodate is fought in Japan.
1871 – The National Association, the first professional baseball league, opens its first season in Fort Wayne, Indiana.
1886 – Haymarket affair: A bomb is thrown at policemen trying to break up a labor rally in Chicago, United States, killing eight and wounding 60. The police fire into the crowd.
1904 – The United States begins construction of the Panama Canal.
1910 – The Royal Canadian Navy is created.
1912 – Italy occupies the Greek island of Rhodes.
1919 – May Fourth Movement: Student demonstrations take place in Tiananmen Square in Beijing, China, protesting the Treaty of Versailles, which transferred Chinese territory to Japan.
1926 – The United Kingdom general strike begins.
1932 – In Atlanta, mobster Al Capone begins serving an eleven-year prison sentence for tax evasion.
1942 – World War II: The Battle of the Coral Sea begins with an attack by aircraft from the United States aircraft carrier USS Yorktown on Japanese naval forces at Tulagi Island in the Solomon Islands. The Japanese forces had invaded Tulagi the day before.
1945 – World War II: Neuengamme concentration camp near Hamburg is liberated by the British Army.
1945 – World War II: The German surrender at Lüneburg Heath includes all Wehrmacht units in the Netherlands, Denmark and northwest Germany.
1946 – In San Francisco Bay, U.S. Marines from the nearby Treasure Island Naval Base stop a two-day riot at Alcatraz Federal Penitentiary; 5 people are killed in the riot.
1949 – The entire Torino football team (except for two players who did not take the trip: Sauro Tomà, due to an injury and Renato Gandolfi, because of coach request) is killed in a plane crash.
1953 – Ernest Hemingway wins the Pulitzer Prize for The Old Man and the Sea.
1959 – The 1st Annual Grammy Awards are held.
1961 – American civil rights movement: The "Freedom Riders" begin a bus trip through the South.
1961 – Malcolm Ross and Victor Prather attain a new altitude record for manned balloon flight ascending in the Strato-Lab V open gondola to 113,740 feet (34.67 km).
1970 – Vietnam War: Kent State shootings: The Ohio National Guard, sent to Kent State University after disturbances in the city of Kent the weekend before, opens fire killing four unarmed students and wounding nine others. The students were protesting the Cambodian Campaign of the United States and South Vietnam.
1972 – The Don't Make A Wave Committee, a fledgling environmental organization founded in Canada in 1971, officially changes its name to "Greenpeace Foundation".
1978 – The South African Defence Force attacks a SWAPO base at Cassinga in southern Angola, killing about 600 people.
1979 – Margaret Thatcher becomes the first female Prime Minister of the United Kingdom.
1982 – Twenty sailors are killed when the British Type 42 destroyer HMS Sheffield is hit by an Argentinian Exocet missile during the Falklands War.
1988 – The PEPCON disaster rocks Henderson, Nevada, as tons of Space Shuttle fuel detonate during a fire.
1989 – Iran–Contra affair: Former White House aide Oliver North is convicted of three crimes and acquitted of nine other charges; the convictions are later overturned on appeal.
1990 – Latvia proclaims the renewal of its independence after the Soviet occupation.
1994 – Israeli Prime Minister Yitzhak Rabin and PLO leader Yasser Arafat sign a peace accord, granting self-rule in the Gaza Strip and Jericho.
1998 – A federal judge in Sacramento, California, gives "Unabomber" Theodore Kaczynski four life sentences plus 30 years after Kaczynski accepts a plea agreement sparing him from the death penalty.
2000 – Ken Livingstone becomes the first Mayor of London.
2007 – Greensburg, Kansas is almost completely destroyed by a 1.7 mi wide EF5 tornado. It was the first-ever tornado to be rated as such with the new Enhanced Fujita scale.
2014 – Three people are killed and 62 injured in a pair of bombings on buses in Nairobi, Kenya.
