1500 - Portuguese navigator Pedro Álvares Cabral becomes the first European to sight Brazil.
1529 - Treaty of Saragossa divides the eastern hemisphere between Spain and Portugal along a line 297.5 leagues or 17° east of the Moluccas.
1809 - The second day of the Battle of Eckmühl sees the Austrian army defeated by the First French Empire army led by Napoleon I of France and driven over the Danube at Regensburg.
1836 - Texas Revolution: A day after the Battle of San Jacinto, forces under Texas General Sam Houston capture Mexican General Antonio López de Santa Anna.
1863 - American Civil War: Grierson's Raid begins – troops under Union Army Colonel Benjamin Grierson attack central Mississippi.
1864 - The United States Congress passes the Coinage Act, mandating that the inscription "In God We Trust" be placed on all coins minted as United States currency.
1889 - At high noon, thousands rush to claim land in the Land Run 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 United States Navy begins a blockade of Cuban ports and the USS;Nashville captures a Spanish merchant ship.
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 - 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. 520 are killed and 80 escape.
1945 - World War II: Fuehrerbunker: 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.
1954 - Red Scare: The Army-McCarthy Hearings begin.
1964 - The 1964-1965 New York World's Fair opens for its first season.
1969 - British yachtsman Sir Robin Knox-Johnston 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.
1979 - The Albert Einstein Memorial is unveiled at The National Academy of Sciences in Washington, DC.
1983 - The German magazine Der Stern claims that the "Hitler Diaries" had been found in wreckage in East Germany; the diaries are subsequently revealed to be forgeries.
1991 - The Social Democratic Party of Albania is founded.
1992 - In an explosion in Guadalajara, Mexico, 206 people are killed, nearly 500 injured and 15,000 left homeless.
1993 - The Holocaust Memorial Museum in Washington, D.C. is dedicated.
1993 - Version 1.0 of the Mosaic web browser is released.
1997 - Haouch Khemisti massacre in Algeria – 93 villagers 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, Florida.
2000 - The Big Number Change takes place in the United Kingdom.
2000 - Second Battle of Elephant Pass, Tamil Tigers capture a strategic Sri Lankan Army base and hold it for 8 years.
2004 - Two fuel trains collide in Ryongchon, North Korea, killing up to 150 people.
2006 - 243 people are injured in pro-democracy protest in Nepal after Nepali security forces open fire on protesters against King Gyanendra.
2006 - Four Canadian soldiers are killed 75 kilometers north of Kandahar, Afghanistan by a roadside bomb planted by Taliban militants, the worst single day combat loss for the Canadian army since the Korean War.
2008 - The United States Air Force retires the remaining F-117 Nighthawk aircraft in service.