On this day: 21 April

According to the calculations of the ancient Roman scholar Varro Reatinus, Romulus and Remus legendarily founded the city of Rome.

A debt was pardoned by the chief of Tondo on the island of Luzon and recorded on the Laguna Copperplate Inscription, the earliest known calendar-dated document found in the Philippines.

The Diocese of Pisa is elevated to the rank of metropolitan archdiocese by Pope Urban II.

The Wignacourt Aqueduct (pictured) in Malta was inaugurated, and was used to carry water to Valletta for about 300 years.

J. S. Bach's cantata Bleib bei uns, denn es will Abend werden, was first performed on Easter Monday.

The city of Rattanakosin, now known internationally as Bangkok, is founded on the eastern bank of the Chao Phraya River by King Buddha Yodfa Chulaloke.

John Adams sworn in as first US Vice President (nine days before George Washington).

The Ladies of Trenton social club hosted a reception for President-elect George Washington as he journeyed to New York City for his first inauguration.

War of the First Coalition: In the climax of the Montenotte Campaign, Napoleon Bonaparte decisively defeats the army of Piedmont at the Battle of Mondovi, leading to Piedmont's surrender a week later and decisively turning the Italian campaign in France's favor.

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.

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.

Forces of the Republic of Texas led by Sam Houston defeated the Mexican troops of Antonio López de Santa Anna in the Battle of San Jacinto, the decisive and final battle of the Texas Revolution.

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.

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.

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.

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

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

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

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.

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

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

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.

Brasília, a planned city primarily designed by architect and urban planner Lúcio Costa, was officially inaugurated, replacing Rio de Janeiro as the capital of Brazil.

The Century 21 Exposition, the first world's fair in the United States since World War II, opened in Seattle.

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

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

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

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.

In response to a dispute over wheat production quotas, Leonard Casley declared his 75 km2 (29 sq mi) farm in Western Australia to be an independent country as the Hutt River Province.

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.

South Vietnamese president Nguyễn Văn Thiệu resigned on hearing of the fall of Xuân Lộc, the last battle of the Vietnam War.

Annie opens on Broadway.

Baseball: Rollie Fingers of the Milwaukee Brewers becomes the first pitcher to record 300 saves.

Tiananmen Square protests of 1989: In Beijing, around 100,000 students gather in Tiananmen Square to commemorate Chinese reform leader Hu Yaobang.

Ukraine and Russia signed the Kharkiv Pact, extending the Russian lease on naval facilities in Crimea.

The city of Flint, Michigan, U.S., changed its water source to the Flint River, which exposed residents to lead poisoning.a