Pericles, the Athenian leader who steered the city through its greatest cultural flowering, funding the Parthenon and championing radical democracy, died as a plague epidemic ravaged war-crowded Athens. His death, coming soon after he lost two sons to the same outbreak, removed the one figure capable of restraining Athens's wartime ambitions, and the city's fortunes in the Peloponnesian War declined markedly without him.
On April 20, Romans across the empire celebrated the Parilia, the traditional founding date of Rome in 753 BC, with bonfires, purification rites, and feasts honoring Pales, goddess of shepherds. In Pompeii and Herculaneum, the festival unfolded in blissful ignorance of the catastrophe brewing beneath Vesuvius, which would erupt within days and entomb both towns.
Hernán Cortés founded the settlement of Villa Rica de la Vera Cruz on the Gulf coast of Mexico, formally asserting Spanish authority independent of the governor of Cuba who had commissioned his expedition. The move gave Cortés legal cover to march inland toward Tenochtitlan, beginning a campaign that within two years would topple the Aztec Empire and reshape the Americas.
The Washington National Monument Society settled on architect Robert Mills's design for a monument to the first U.S. president, a towering obelisk originally conceived with an elaborate colonnaded base. Funding troubles, the Civil War, and political infighting would stall construction for decades; the visible color change partway up the finished monument still marks where work paused for 23 years.
Adolf Hitler was born to Alois and Klara Hitler in the small Austrian town of Braunau am Inn, on the border with Bavaria. An unremarkable, artistically inclined youth who twice failed entry to Vienna's Academy of Fine Arts, he would go on to found the Nazi movement, seize dictatorial power in Germany, and orchestrate the Holocaust and a war that killed tens of millions.
Apollo 16's lunar module Orion touched down in the Descartes highlands, a mountainous region chosen specifically because scientists expected to find volcanic rock there. John Young and Charles Duke instead discovered the area was built from ancient impact breccia, an unexpected result that reshaped understanding of the Moon's geologic history, while Ken Mattingly orbited above in the command module Casper.
Eric Harris and Dylan Klebold, armed with guns and homemade explosives, attacked Columbine High School, killing 13 people and wounding 21 before dying by suicide. The massacre, then the deadliest school shooting in U.S. history, became a grim national reference point, reshaping school security policy and dominating American debates over gun violence, bullying, and media coverage for years afterward.
A sudden blowout of methane gas aboard the Deepwater Horizon drilling rig triggered explosions and fire, killing 11 crew members and sinking the platform two days later. The ruptured wellhead, a mile beneath the surface, gushed roughly 4.9 million barrels of oil over 87 days, devastating Gulf Coast ecosystems and fisheries and prompting sweeping changes to offshore drilling regulation.