April 17

Spain and Christopher Columbus sign the Capitulations of Santa Fe, laying out the terms of his planned westward voyage in search of a new route to Asia.

Spanish monarchs Ferdinand and Isabella signed the Capitulations of Santa Fe with Christopher Columbus, granting him noble titles, a share of future profits, and governance rights over any lands he discovered in exchange for undertaking his westward voyage in search of a new trade route to Asia. The agreement financed the expedition that, months later, reached the Americas.

Martin Luther's trial before the Diet of Worms begins over his religious writings challenging the Catholic Church.

Reformer Martin Luther appeared before the Diet of Worms, an assembly of the Holy Roman Empire, to answer charges of heresy over his writings challenging Catholic Church doctrine and practices. Luther's refusal to recant, reportedly declaring "here I stand, I can do no other," became a defining moment of the Protestant Reformation, though the assembly ultimately declared him an outlaw.

Italian explorer Giovanni da Verrazzano becomes the first European to sail into New York Harbor.

Italian explorer Giovanni da Verrazzano, sailing under the French flag, became the first European recorded to enter New York Harbor, describing the area's natural beauty in his subsequent report to King Francis I. The Verrazzano-Narrows Bridge in New York was later named in his honor, though the Dutch would not establish a permanent settlement in the region for another century.

Virginia's secession convention votes to leave the Union, becoming the eighth state to join the Confederacy.

Virginia's secession convention voted to leave the Union following President Lincoln's call for troops to suppress the rebellion after the attack on Fort Sumter, making Virginia the eighth state to join the Confederacy. The decision led directly to the western counties of the state splitting off to remain loyal to the Union, eventually forming the separate state of West Virginia.

The Treaty of Shimonoseki ends the First Sino-Japanese War, with China ceding Taiwan and other territory to Japan.

China and Japan signed the Treaty of Shimonoseki, ending the First Sino-Japanese War with a decisive Japanese victory that forced the weakened Qing dynasty to cede Taiwan, the Penghu Islands, and other territory while recognizing Korean independence. The treaty marked Japan's emergence as a major regional power and accelerated the decline of Chinese imperial influence in East Asia.

CIA-trained Cuban exiles launch the failed Bay of Pigs Invasion in an attempt to overthrow Fidel Castro's government.

A brigade of roughly 1,400 CIA-trained Cuban exiles launched an amphibious invasion at Cuba's Bay of Pigs, intending to spark a popular uprising against Fidel Castro's government. The poorly coordinated operation collapsed within days against determined Cuban resistance, embarrassing the recently inaugurated Kennedy administration and pushing Castro further into the Soviet orbit.

The crippled Apollo 13 spacecraft returns safely to Earth after its harrowing journey around the Moon.

The damaged Apollo 13 spacecraft, its crew having endured a harrowing four-day ordeal after an oxygen tank explosion crippled the vessel en route to the Moon, splashed down safely in the Pacific Ocean, to the immense relief of NASA and a worldwide television audience. The mission's successful, improvised rescue became one of the space agency's most celebrated achievements.

Khmer Rouge forces capture Phnom Penh, ending the Cambodian Civil War and beginning a brutal genocidal regime.

Khmer Rouge forces captured the Cambodian capital of Phnom Penh, ending the country's civil war but beginning a brutal four-year totalitarian regime under Pol Pot that forcibly evacuated cities and caused the deaths of an estimated one to two million Cambodians through executions, starvation, and forced labor in what became known as the Killing Fields.

Queen Elizabeth II proclaims Canada's new constitution, completing the country's full legal independence from Britain.

Queen Elizabeth II traveled to Ottawa to formally proclaim Canada's new constitution, which included a domestic amending formula and the Canadian Charter of Rights and Freedoms, completing the process known as "patriation" that ended the need for British parliamentary approval of Canadian constitutional changes. The event marked Canada's full legal independence from the United Kingdom.

A fertilizer plant explosion in West, Texas, kills 15 people and injures more than 160 others.

An explosion at a fertilizer storage and distribution facility in the small town of West, Texas, killed 15 people, mostly first responders, and injured more than 160 others, leveling much of the surrounding area including a nearby school and nursing home. The disaster prompted renewed scrutiny of chemical storage regulations and emergency response protocols for hazardous facilities.