April 21 in history — What Happened Today in History

Vietnam War: President of South Vietnam Nguyễn Văn Thiệu flees Saigon, as Xuân Lộc, the last South Vietnamese outpost blocking a direct North Vietnamese assault on Saigon, falls.

Astronauts John Young and Charles Duke fly Apollo 16's Apollo Lunar Module to the Moon's surface, the fifth NASA Apollo Program crewed lunar landing.

A few days before the general election in Greece, Colonel George Papadopoulos leads a coup d'état, establishing a military regime that lasts for seven years.

A tornado outbreak in Illinois, United States, kills over 50 and injures over 1,000. Belvidere sustains over 500 casualties as a violent tornado strikes the high school. Another tornado near Chicago causes another 500 casualties, devastating Oak Lawn.

Rastafari movement: Haile Selassie of Ethiopia visits Jamaica, an event now celebrated as Grounation Day.

The 1964–1965 New York World's Fair opens for its second and final season.

A Transit-5bn satellite fails to reach orbit after launch; as it re-enters the atmosphere, 2.1 pounds (0.95 kg) of radioactive plutonium in its SNAP RTG power source is widely dispersed.

The first election of the Universal House of Justice is held, marking its establishment as the supreme governing institution of the Baháʼí Faith.

The Seattle World's Fair (Century 21 Exposition) opens. It is the first World's Fair in the United States since World War II.

Brasília, Brazil's capital, is officially inaugurated. At 09:30, the Three Powers of the Republic are simultaneously transferred from the old capital, Rio de Janeiro.

United Air Lines Flight 736 collides with a United States Air Force fighter jet near Arden, Nevada in what is now Enterprise, Nevada.

Secretary's Day (now Administrative Professionals' Day) is first celebrated.

The Nainital wedding massacre occurs, killing 22 members of the Harijan caste.

United Nations Security Council Resolution 47 relating to Kashmir conflict is adopted.

The U.S. Weather Bureau records that a tornado which struck Timber Lake, South Dakota was 4 miles (6.4 km), among the widest tornadoes on record.

World War II: Soviet forces south of Berlin at Zossen attack the German High Command headquarters.

The "Surgeon's Photograph", the most famous photo allegedly showing the Loch Ness Monster, is published in the Daily Mail (in 1994, it is revealed to be a hoax).

Al-Baqi cemetery, former site of the mausoleum of four Shi'a Imams, is leveled to the ground by Wahhabis.

World War I: German fighter ace Manfred von Richthofen, better known as "The Red Baron", is shot down and killed over Vaux-sur-Somme in France.

Ypiranga incident: A German arms shipment to Mexico is intercepted by the U.S. Navy near Veracruz.

Spanish–American War: The United States Navy begins a blockade of Cuban ports. When the U.S. Congress issued a declaration of war on April 25, it declared that a state of war had existed from this date.

Norway formally adopts the Krag–Jørgensen bolt-action rifle as the main arm of its armed forces, a weapon that would remain in service for almost 50 years.

Australian labour movement: Stonemasons and building workers on building sites around Melbourne march from the University of Melbourne to Parliament House to achieve an eight-hour day.

Texas Revolution: The Battle of San Jacinto: Republic of Texas forces under Sam Houston defeat troops under Mexican General Antonio López de Santa Anna.

Benderli Ali Pasha arrives in Constantinople as the new Grand Vizier of the Ottoman Empire; he remains in power for only nine days before being sent into exile.

Two Austrian army corps are driven from Landshut by a First French Empire army led by Napoleon as two French corps to the north hold off the main Austrian army on the first day of the Battle of Eckmühl.

Action of 21 April 1806: A French frigate escapes British forces off the coast of South Africa.

Twelve thousand Wahhabis sack Karbala, killing over three thousand inhabitants.

Nikki Cross, Scottish wrestler

Ricky Berens, American swimmer

Jencarlos Canela, American singer-songwriter and actor

Christoph Sanders, American actor

Tarvaris Jackson, American football player (died 2020)

Kim Wall, British sprinter

Tony Romo, American football player and announcer

Virginie Basselot, French chef

James McAvoy, Scottish actor

Gyula Koi, Hungarian scholar and educator

Jamie Salé, Canadian figure skater

Petero Civoniceva, Fijian-Australian rugby league player

Danyon Loader, New Zealand swimmer

Gustav Lorentzen, Norwegian singer-songwriter and guitarist (born 1947)

Juan Antonio Samaranch, Spanish businessman, seventh President of the International Olympic Committee (born 1920)

Kanagaratnam Sriskandan, Sri Lankan-English engineer and civil servant (born 1930)

Zhang Chunqiao, Chinese writer and politician, member of the Gang of Four (born 1917)

Nina Simone, American singer-songwriter, pianist, and activist (born 1933)

Buddy Rogers, American actor (born 1904)

Jean-François Lyotard, French sociologist and philosopher (born 1924)

Diosdado Macapagal, Filipino lawyer and politician, 9th President of the Philippines (born 1910)

Abdul Hafeez Kardar, Pakistani cricketer (born 1925)

Jimmy Snyder, American sportscaster (born 1919)

Väinö Linna, Finnish author (born 1920)

Willi Boskovsky, Austrian violinist and conductor (born 1909)

Erté, Russian-French illustrator (born 1892)