238 – Year of the Six Emperors: The Roman Senate outlaws emperor Maximinus Thrax for his bloodthirsty proscriptions in Rome and nominates two of its members, Pupienus and Balbinus, to the throne.
1500 – Portuguese navigator Pedro Álvares Cabral lands in Brazil.
1519 – Spanish conquistador Hernán Cortés establishes a settlement at Veracruz, Mexico.
1529 – Treaty of Zaragoza divides the eastern hemisphere between Spain and Portugal along a line 297.5 leagues or 17° east of the Moluccas.
1622 – The Capture of Ormuz by the East India Company ends Portuguese control of Hormuz Island.
1809 – The second day of the Battle of Eckmühl: The Austrian army is defeated by the First French Empire army led by Napoleon I of France and driven over the Danube in Regensburg.
1836 – Texas Revolution: A day after the Battle of San Jacinto, forces under Texas General Sam Houston identify Mexican General Antonio López de Santa Anna among the captives of the battle when one of his fellow captives mistakenly gives away his identity.
1864 – The U.S. Congress passes the Coinage Act of 1864 that mandates that the inscription In God We Trust be placed on all coins minted as United States currency.
1876 – The first ever National League baseball game is played in Philadelphia.
1889 – At high noon, thousands rush to claim land in the Land Rush of 1889. Within hours the cities of Oklahoma City and Guthrie are formed with populations of at least 10,000.
1898 – Spanish–American War: The USS Nashville captures a Spanish merchant ship.
1906 – The 1906 Summer Olympics, not now recognized as part of the official Olympic Games, open in Athens.
1911 – Tsinghua University, one of mainland China's leading universities, is founded.
1912 – Pravda, the "voice" of the Communist Party of the Soviet Union, begins publication in Saint Petersburg.
1915 – The use of poison gas in World War I escalates when chlorine gas is released as a chemical weapon in the Second Battle of Ypres.
1930 – The United Kingdom, Japan and the United States sign the London Naval Treaty regulating submarine warfare and limiting shipbuilding.
1944 – The 1st Air Commando Group using Sikorsky R-4 helicopters stage the first use of helicopters in combat with combat search and rescue operations in the China-Burma-India theater.
1944 – World War II: Operation Persecution is initiated: Allied forces land in the Hollandia (currently known as Jayapura) area of New Guinea.
1945 – World War II: Prisoners at the Jasenovac concentration camp revolt. Five hundred twenty are killed and 80 escape.
1945 – World War II: Führerbunker: After learning that Soviet forces have taken Eberswalde without a fight, Adolf Hitler admits defeat in his underground bunker and states that suicide is his only recourse.
1948 – 1948 Arab–Israeli War: Haifa, a major port of Israel, is captured from Arab forces.
1951 – Korean War: The Chinese People's Volunteer Army begin assaulting positions defended by the Royal Australian Regiment and the Princess Patricia's Canadian Light Infantry at the Battle of Kapyong.
1954 – Red Scare: Witnesses begin testifying and live television coverage of the Army–McCarthy hearings begins.
1964 – The 1964-1965 New York World's Fair opens for its first season.
1969 – British yachtsman Sir Robin Knox-Johnston wins the Sunday Times Golden Globe Race and completes the first solo non-stop circumnavigation of the world.
1970 – The first Earth Day is celebrated.
1972 – Vietnam War: Increased American bombing in Vietnam prompts anti-war protests in Los Angeles, New York City, and San Francisco.
1977 – Optical fiber is first used to carry live telephone traffic.
1983 – The German magazine Stern claims that the "Hitler Diaries" had been found in wreckage in East Germany; the diaries are subsequently revealed to be forgeries.
1992 – In an explosion in Guadalajara, Mexico, 206 people are killed, nearly 500 injured and 15,000 left homeless.
1993 – Version 1.0 of the Mosaic web browser is released.
1997 – Haouch Khemisti massacre in Algeria where 93 villagers are killed.
1997 – The Japanese embassy hostage crisis ends in Lima, Peru.
1998 – Disney's Animal Kingdom opens at Walt Disney World near Orlando, Florida, United States.
2000 – In a pre-dawn raid, federal agents seize six-year-old Elián González from his relatives' home in Miami.
2000 – The Big Number Change takes place in the United Kingdom.
2004 – Two fuel trains collide in Ryongchon, North Korea, killing up to 150 people.
2005 – Japan's Prime Minister Junichiro Koizumi apologizes for Japan's war record.
2008 – The United States Air Force retires the remaining F-117 Nighthawk aircraft in service.
2013 – Six people die in a shooting in Belgorod, Russia.
2013 – The Royal Canadian Mounted Police arrest and charge two men with plotting to disrupt a Toronto area train service in a plot claimed to be backed by Al-Qaeda elements.
2014 – More than 60 people are killed and 80 are seriously injured in a train crash in the Democratic Republic of the Congo's Katanga Province.