History of the Day for:
April 21
- 1649: The Maryland Assembly passed the Maryland Toleration Act, guaranteeing freedom of worship for all Christians.
- 1789: John Adams was sworn in as the first vice president.
- 1836: Sam Houston, leading an army of Texans, defeated the Mexicans at San Jacinto, assuring Texas independence.
- 1837: Friedrich Froebel founded the first kindergarten in Blankenburg, Germany.
- 1855: The first train crossed the Mississippi River's first bridge, from Rock Island, Ill., to Davenport, Iowa.
- 1910: Author Mark Twain, died in Redding, Conn.
- 1918: Baron Manfred von Richthofen, the "Red Baron" German flying ace, was shot down and killed in action.
- 1940: The quiz show "Take It or Leave It" premiered on CBS Radio.
- 1942: World War II: The most famous (and first international) Aggie Muster is held on the Philippine island of Corregidor, by Brigadier General George F. Moore (with 25 fellow Aggies who are under his command), while 1.8 million pounds of shells pounded the island over a 5 hour attack.
- 1945: World War II: Soviet Union forces south of Berlin at Zossen attack the German High Command headquarters.
- 1960: Brazil established its new capital, Brasilia, moving the government from Rio de Janeiro.
- 1972: Apollo 16 astronauts John Young and Charles Duke explored the moon by driving an electric car called the LEM.
- 1975: South Vietnamese President Nguyen Van Thieu resigned.
- 1977: The musical "Annie" opened on Broadway.
- 1982: Rollie Fingers of the Milwaukee Brewers becomes the first pitcher to record 300 saves.
- 1987: The Tamil Tigers are blamed for a car bomb that explodes in the Sri Lankan city of Colombo, killing 106 people.
- 1989: Tiananmen Square Protests of 1989: In Beijing, around 100,000 students gather in Tiananmen Square to commemorate Chinese reform leader Hu Yaobang.
- 1993: The Supreme Court in La Paz, Bolivia, sentences former dictator Luis Garcia Meza to 30 years in jail without parole for murder, theft, fraud and violating the constitution.
- 1994: The first discoveries of extrasolar planets are announced by astronomer Alexander Wolszczan.