This Day In History, April 20th

What happened on this day in history: Adolf Hitler is born, Marie and Pierre Curie isolate radium, and other important events that happened on April 20.

1689: The Siege Of Derry Begins

Today In History April 20

Culture Club/Getty ImagesA 17th-century depiction of the Siege of Derry.

The siege of Derry begins in Ireland. Started by James II, the recently deposed King of England, the siege lasted for 105 days and pitted James’s Catholic supporters against the Crown-supporting Protestants of Derry. The siege ended in August with the arrival of British troops.

1889: Adolf Hitler Is Born In Austria

Adolf Hitler is born to Alois and Klaire Hitler in Braunau am Inn, Austria. The leader of the Nazi party, Hitler was one of the main architects of the Holocaust, which killed an estimated 11 million people during World War II, including six million Jews. He died by suicide when Germany was on the brink of losing World War 2, taking his own life in his Berlin bunker on April 30, 1945.

1902: Marie And Pierre Curie Isolate Radium

Marie Curie

Bettmann/Getty ImagesMarie Curie in her lab, circa 1905.

Marie Curie and her husband Pierre isolate radium. The radioactive material was originally thought to have curative properties, and it was used in items like wristwatches to make them glow in the dark. It wasn’t until later that radium was found to be dangerous, and Curie herself died from leukemia after four decades of working with radioactive materials.

1999: The Columbine School Shooting

Columbine School Shooting

Jefferson County Sheriff’s Department via Getty ImagesColumbine high school shooters Eric Harris and Dylan Klebold in a surveillance tape in the cafeteria at Columbine High School.

A mass shooting takes place at Columbine High School in Littleton, Colorado. During the Columbine High School shooting, 18-year-old Eric Harris and 17-year-old Dylan Klebold killed 13 people and injured 20 more before both gunmen died by suicide. At the time, it was the deadliest school shooting in American history.

2010: The Deepwater Horizon Oil Spill Takes Place

The oil drilling rig Deepwater Horizon explodes in the Gulf of Mexico. Eleven workers were killed and the subsequent oil spill was the largest in recorded history. Four million barrels of oil poured from the rig for almost 90 days before the spill was finally capped in July 2010.