On this day in history April 21,
- 1970 – The Hutt River Province Principality secedes from Australia.
- 1975 – Vietnam War: President of South Vietnam Nguyen Van Thieu flees Saigon, as Xuan Loc, the last South Vietnamese outpost blocking a direct North Vietnamese assault on Saigon, falls.
- 1982 – Baseball: 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 detonates in the Sri Lankan capital 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.
- 1992 – The first discoveries of extrasolar planets are announced by astronomers Alexander Wolszczan and Dale Frail. They discovered two planets orbiting the pulsar PSR 1257+12.
- 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.