March 21st

Russia formally annexes Crimea amid international condemenation.
Timeline of the annexation of Crimea by the Russian Federation ...
The House of Representatives passes a bill that will overhaul the American health-care system. The bill, called the Patient Protection and Affordable Care Act, will be sent to President Obama to sign into law.
Patient Protection and Affordable Care Act
Jack Dorsey sends the world's first Twitter message, or tweet. The microblogging service revolutionized the communication and social networking landscape. In 2012, about 340 million tweets were posted per day.
A divided Supreme Court ruled the government lacked authority to regulate tobacco as an addictive drug.
Tobacco Master Settlement Agreement
The album 'The Joshua Tree' by U2 was released.
The Joshua Tree
South African Police kill at least 21 black people commemorating a similar mass shooting 25 years before. The Sharpeville massacre in 1985 had left 69 unarmed people dead. It was a turning-point in the history of South Africa.
Sharpeville massacre
Ethiopia abolishes its monarchy after 3,000 years.
Ethiopian Empire
Earth Day is celebrated for the first time. The first edition was limited to some cities in the United States. Today, Earth Day is observed by about 1 billion people around the world.
Earth Day
Martin Luther King, Jr., led the start of a civil rights march from Selma to Montgomery, Alabama.
Selma to Montgomery marches
Alcatraz Prison in San Francisco Bay, a harsh maximum security jail which once housed gangster Al Capone, closed.
Police fired on demonstrators in Sharpeville, South Africa, after which the African National Congress was banned. 25 years later, a march marking the anniversary was also disrupted by police fire.
Sharpeville massacre
The world's first rock and roll concert is held in Cleveland, Ohio. DJ Alan Freed presented the concert, which was closed down after only one song because of over-crowding.
Moondog Coronation Ball
A plot to assassinate Adolf Hitler by suicide bomb fails. German Wehrmacht officer, Rudolf von Gersdorff, failed to blow up the dictator but managed to defuse his bombs just before they went off and avoid suspicion.
Rudolf Christoph Freiherr von Gersdorff
Germany launched the Somme offensive during World War I, hoping to break through the Allied line before American reinforcements could arrive.
Spring Offensive
Journalist Henry M. Stanley began his trek to find the missionary and explorer David Livingstone.
Henry Morton Stanley
The French civil code, the Code Napoleon, was officially put forth.
Napoleonic Code
Thomas Jefferson took office as America's first secretary of state.
Thomas Jefferson
Composer Johann Sebastian Bach was born in Eisenach, Germany.
Johann Sebastian Bach
The Archbishop of Canterbury, Thomas Cranmer, was burned at the stake as a heretic.
Thomas Cranmer
3,000 Jews killed in Black Death riots in Efurt, Germany.
Erfurt massacre (1349)