April 20th

2010
The Deepwater Horizon oil rig explodes. The explosion of the British Petroleum (BP) platform operated by Transocean killed 11 workers and led to the largest accidental marine oil spill in history.
Deepwater Horizon explosion
2008
Danica Patrick became the first female winner in IndyCar history by capturing the Indy Japan 300.
Danica Patrick
1999
15 die in the Columbine High School massacre. A further 24 victims were injured when two teenagers opened fire on students and teachers in the high school south of Denver.
Columbine High School massacre
1980
The first Cubans sailing to the United States as part of the massive Mariel boatlift reached Florida.
Mariel boatlift
1978
Soviet air defense shoots down Korean Air Lines Flight 902. The Boeing 707's crew had miscalculated their route, taking them into Soviet air space at the height of the Cold War. The jet made an emergency landing on a frozen lake. Two passengers were killed in the incident.
Korean Air Lines Flight 902
1974
'The Troubles', the Northern Ireland conflict between republican and loyalist paramilitaries, British security forces, and civil rights groups, claims its 1000th victim.
The Troubles
1972
The manned lunar module from Apollo 16 landed on the moon.
Apollo 16
1971
The U.S. Supreme Court upheld the use of busing to achieve racial desegregation in schools.
Desegregation busing
1968
British politician Enoch Powell makes his controversial "Rivers of Blood" speech.
Rivers of Blood speech
1951
A human organ is surgically replaced for the first time. Romanian surgeon Dan Gavriliu used a section of the stomach to bypass the esophagus.
Dan Gavriliu
1940
RCA publicly demonstrated its new electron microscope.
RCA
1939
Baseball Hall of Famer Ted Williams made his major league debut with the Boston Red Sox.
Ted Williams
1920
Balfour Declaration recognized, makes Palestine a British Mandate.
Balfour Declaration
1912
The Boston Red Sox played their first game at Fenway Park. They beat the N.Y. Highlanders (who in 1913 would become known as the Yankees) 7-6.
New York Yankees
1902
Pierre and Marie Curie discover the radioactive element radium. In 1903, the French couple received the Nobel Prize in Physics for their pioneering research.
Marie Curie
1889
Nazi leader Adolf Hitler was born in Braunau, Austria.
Adolf Hitler
1862
First pasteurization test completed by Frenchmen Louis Pasteur and Claude Bernard.
Louis Pasteur
1841
The first detective story, Edgar Allen Poe's Murders in the Rue Morgue was published.
The Murders in the Rue Morgue
1836
The Territory of Wisconsin was established by Congress.
Wisconsin Territory
1812
Vice President George Clinton, a former New York governor, died at age 73.
George Clinton (vice president)
1792
France declared war on Austria, marking the start of the French Revolutionary wars.
French Revolutionary Wars
1769
Ottawa Indian chief Pontiac murdered.
Pontiac (Ottawa leader)