In 1509, King Henry VII of England died; his 17-year-old son, Henry VIII, succeeded him.
In 1649, the Maryland Toleration Act, providing freedom of worship for all Christians, was passed by the Maryland assembly.
In 1789, John Adams was sworn in as the first vice president of the United States.
In 1836, a Texan army led by Sam Houston defeated the Mexicans at San Jacinto, securing Texas' independence.
In 1910, author Samuel Langhorne Clemens, better known as Mark Twain, died in Redding, Connecticut at the age of 74.
In 1918, 25-year-old Manfred von Richthofen, the German ace known as the Red Baron, who is said to have shot down 80 enemy planes during World War I, was himself shot down and killed while fighting over France.
In 1926, Queen Elizabeth II of Great Britain was born in Mayfair, London; she was the first child of the Duke and Duchess of York, who later became King George VI and the Queen Mother.
In 1930, a fire broke out in the overcrowded Ohio State Penitentiary in Columbus, killing 332 inmates.
In 1942, the first edition of The Stranger (LEtranger), a highly influential absurdist novel by Albert Camus, was published in Nazi-occupied Paris.
In 1955, Jerome Lawrence Robert Lee's play Inherit the Wind, inspired by the Scopes trial of 1925, premiered at the National Theater in New York.
In 1960, the new city of Brasilia officially became the capital of Brazil.
In 1962, the Century 21 Expo, also known as the Seattle World's Fair, began a six-month run.
In 1975, as communist forces closed in, South Vietnamese President Nguyen Van Thieu resigned after nearly 10 years in office and fled the country.
In 1976, clinical trials of the swine flu vaccine began in Washington, DC.
In 1977, the musical Annie, based on the comic strip Little Orphan Annie, premiered on Broadway; it ran for 2,377 performances.
In 1986, a rediscovered safe in Chicago's Lexington Hotel, linked to Al Capone, was opened during a widely watched live television broadcast hosted by Geraldo Rivera; apart from a few bottles and a sign, the safe turned out to be empty.
In 1992, murderer Robert Alton Harris became the first person executed by the state of California in 25 years.
In 1998, astronomers announced in Washington that they had discovered possible signs of a new family of planets orbiting a star 220 light years away, the clearest evidence yet of the formation of worlds beyond our solar system.
In 2013, Joe Scarborough, a 50-year-old independent electrical contractor, pitched the first 900 Series in Professional Bowlers Association history, with three consecutive perfect games.
In 2015, an Egyptian criminal court sentenced ousted Islamist president Mohammed Morsi to 20 years in prison for the killing of protesters in 2012.
In 2016, Prince, one of the most inventive and influential musicians of modern times, was found dead at his home in suburban Minneapolis; he was 57 years old.
In 2021, an Indonesian submarine with 53 crew members on board disappeared after its last reported dive off the resort island of Bali; officials later concluded that the submarine had sunk and broken up, killing all on board.
In 2022, CNN shut down its CNN+ streaming service less than a month after its launch. Russian President Vladimir Putin has claimed victory in the battle for the Ukrainian city of Mariupol.
TODAY'S FACT: April 21, 753 BC is traditionally considered the date of the founding of Rome by the mythological twins Romulus and Remus.
TODAY'S SPORTS: In 1980, Rosie Ruiz won the women's division of the Boston Marathon; the title was stripped eight days later when officials learned that Ruiz had started the race just a mile before the finish line. Canadian Jacqueline Gareau was named the true winner of the women's race.
NUMBER TODAY: 70 years — Queen Elizabeth II ruled Britain, making her the longest-reigning monarch in the country's history.