April 19

The Lisbon Massacre begins, in which thousands of forcibly converted Jews are killed by a mob over several days.

A mob in Lisbon, incited by rumors and religious fervor, began a massacre of thousands of Jewish residents who had been forcibly converted to Christianity under earlier Portuguese decrees, killing victims over several days of violence before royal authorities finally intervened to restore order. The massacre remains one of the darkest episodes in Portuguese history.

A group of reform-minded rulers formally protest the reinstatement of the Edict of Worms at the Second Diet of Speyer, an act that gave rise to the term "Protestant."

A group of reform-minded German princes and free cities formally protested the Diet of Speyer's decision to reinstate restrictions on the Edict of Worms, which had earlier suppressed Martin Luther's teachings, an act of defiance that gave rise to the term "Protestant" used to describe followers of the emerging Reformation movement.

Captain James Cook sights the eastern coast of Australia for the first time.

British explorer Captain James Cook and the crew of HMS Endeavour sighted the eastern coastline of Australia for the first time, beginning a survey voyage that would lead to Cook's later landing and claiming of the territory for Britain. The sighting marked a significant step in European awareness and eventual colonization of the Australian continent.

The American Revolutionary War begins with the Battles of Lexington and Concord, the first military engagements of the conflict.

British regulars marching to seize colonial weapons stockpiles clashed with Massachusetts militiamen at Lexington and Concord in the first military engagements of the American Revolutionary War, an exchange later commemorated as "the shot heard round the world." The fighting, which saw British forces suffer heavy casualties during their retreat to Boston, marked the point of no return toward full-scale rebellion.

Jewish resistance fighters launch the Warsaw Ghetto Uprising as German troops attempt to round up the ghetto's remaining residents for deportation.

Jewish resistance fighters in the Warsaw Ghetto, armed with smuggled and improvised weapons, launched an uprising against German troops attempting a final roundup of the ghetto's remaining residents for deportation to death camps. Though the underequipped fighters were ultimately crushed after nearly a month of fighting, the uprising stands as one of the most significant acts of Jewish resistance during the Holocaust.

Actress Grace Kelly marries Prince Rainier III of Monaco in a lavish ceremony.

Hollywood film star Grace Kelly married Prince Rainier III of Monaco in an elaborate ceremony watched by an estimated global television audience of 30 million people, transforming the American actress into Princess Grace and effectively ending her acting career. The glamorous wedding significantly raised the tiny principality's international profile.

The 51-day standoff at Waco, Texas, ends when a fire breaks out at the Branch Davidian compound, killing 76 people.

A fire of disputed origin engulfed the Branch Davidian compound near Waco, Texas, at the end of a 51-day standoff between the religious sect and federal law enforcement agents, killing 76 people including the group's leader, David Koresh, and many children. The controversial siege and its violent conclusion later influenced extremist movements and fueled deep distrust of federal law enforcement among some Americans.

A truck bomb destroys the Alfred P. Murrah Federal Building in Oklahoma City, killing 168 people in the deadliest act of domestic terrorism in U.S. history.

A truck bomb assembled by Timothy McVeigh detonated outside the Alfred P. Murrah Federal Building in Oklahoma City, killing 168 people, including 19 children in an on-site daycare, in the deadliest act of domestic terrorism in American history. McVeigh, motivated by anti-government extremism, was later convicted and executed for the attack.

Cardinal Joseph Ratzinger is elected pope, taking the name Benedict XVI.

The College of Cardinals elected German Cardinal Joseph Ratzinger as pope, and he took the name Benedict XVI, becoming the first German pontiff in nearly a thousand years. Known for his theological conservatism, Benedict served until his surprise resignation in 2013, becoming the first pope to voluntarily step down in nearly 600 years.

NASA's Ingenuity helicopter achieves the first powered, controlled flight of an aircraft on another planet, Mars.

NASA's small robotic helicopter Ingenuity achieved the first powered, controlled flight of an aircraft on another planet, lifting briefly off the surface of Mars as part of the Perseverance rover mission. The successful test, inspired in part by the Wright brothers' first flight, opened new possibilities for aerial exploration of other worlds.