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Today in History, April 20th

On April 20, 2010, the Deepwater Horizon rig exploded, starting the largest offshore oil spill in U.S. history. Plus the Mariel boatlift.

By Today in History Updated November 10, 2026 3 min read Sources checked

Published April 20, 2026 · Last updated November 10, 2026

April 20 is best known as the day in 2010 when the Deepwater Horizon drilling rig exploded in the Gulf of Mexico, starting the largest offshore oil spill in U.S. history. The date also saw Fidel Castro open the Mariel boatlift in 1980 and Fenway Park host its first game in 1912.

The big story: The Deepwater Horizon Explosion (2010)

On April 20, 2010, the Deepwater Horizon rig was drilling an exploratory well for BP about 50 miles off the Louisiana coast when it exploded and caught fire. Eleven of the 126 people aboard were killed and 17 were badly hurt. Two days later the burning rig sank in roughly 5,000 feet of water, and the well on the seafloor kept gushing. It took until July 15 for BP to cap it temporarily, and the government did not declare it permanently sealed until September 19. By then an estimated 4.9 million barrels of crude had poured into the Gulf, reaching the shores of Louisiana, Mississippi, Alabama and Florida and hammering fishing, tourism and wildlife. A national commission later called the disaster foreseeable and preventable, blaming human error, engineering and management failures, and weak regulation. BP pleaded guilty to criminal charges in 2012 and in 2015 agreed to pay $18.7 billion in fines.

More events on April 20

Year	What happened
1653	Oliver Cromwell dissolved England’s Rump Parliament (Old Style), a step on the road to his Protectorate.
1861	Robert E. Lee resigned from the U.S. Army days after Virginia seceded, even though he had opposed secession.
1871	Congress passed the Ku Klux Klan Act, letting the president use military force against the Klan.
1912	Fenway Park in Boston and Navin Field (later Tiger Stadium) in Detroit hosted their first professional baseball games.
1914	Colorado militiamen attacked a tent colony of striking coal miners at Ludlow. Twenty-five people died, including 11 children.
1971	In Swann v. Charlotte-Mecklenburg Board of Education, the U.S. Supreme Court unanimously upheld busing to desegregate schools.
1980	Fidel Castro announced that Cubans could leave from the port of Mariel, launching a boatlift that brought about 125,000 people to the U.S.
1986	Michael Jordan scored a playoff-record 63 points, though his Chicago Bulls lost to Boston in double overtime.
1999	Two students carried out a mass shooting at Columbine High School in Littleton, Colorado.
2008	Danica Patrick won the Indy Japan 300 at Motegi, the first woman to win an IndyCar race.
2016	The U.S. Treasury announced plans to put Harriet Tubman on the $20 bill in place of Andrew Jackson.

Born on April 20

1808: Napoleon III, president of France’s Second Republic and later emperor of France.
1937: George Takei, American actor best known as Lt. Hikaru Sulu in Star Trek.
1951: Luther Vandross, American soul and pop singer, songwriter and producer.