On this day in history - Today, March, 21

Today in History

• 1943 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

• 1952 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-crowd

• 1970 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 a

• 1985 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 hist

• 2006 Jack Dorsey sends the world's first Twitter message, or tweet

  The microblogging service revolutionized the communication and social networking landscape. In 2012,