MAY

May 15 wasn’t just another square on the calendar.

It has been a day for royal edicts, daring expeditions, artistic debuts, scientific leaps, and the lives of people who left a mark on the story of the world.

World History392

Emperor Valentinian II Found Dead in Gaul

On May 15, 392, the Western Roman emperor Valentinian II was found dead at his residence in Vienne, in present-day France. Ancient sources describe his death as a hanging, and debate has long swirled over whether it was suicide or murder orchestrated by powerful generals like Arbogast. Valentinian had been a Christian ruler installed as a child and steered by advisers amid fierce religious and political struggles. His death opened the door for the usurper Eugenius and accelerated the empire’s internal fractures in the decades before the Western half finally collapsed.

World History1252

Pope Innocent IV Issues the Bull “Ad extirpanda”

On May 15, 1252, Pope Innocent IV promulgated the papal bull Ad extirpanda, aimed at combating heresy in northern Italy. The document authorized secular authorities, in cooperation with the Inquisition, to use certain forms of torture during interrogations, while also setting limits on how far they could go. According to surviving texts, it insisted that the accused could not be killed or permanently maimed, though these restrictions were often interpreted loosely. The bull became a key legal and moral reference point for inquisitorial procedures in late medieval Europe, with consequences that echoed for centuries in debates about religious authority and coercion.

Arts & Culture1536

Anne Boleyn Tried for Treason and Adultery in London

On May 15, 1536, England’s Queen Anne Boleyn was tried in the Tower of London on charges of adultery, incest, and high treason. Presided over by her uncle, the Duke of Norfolk, the trial drew nobles and courtiers who watched as the once-celebrated queen defended herself with what many chroniclers described as striking composure and eloquence. Despite the thin and politically charged evidence, she was found guilty by a jury of peers. Her downfall—driven by Henry VIII’s desire for a male heir and a new marriage—reshaped the Tudor court and has fueled plays, novels, films, and historical debates about power, gender, and reputation ever since.

World History1618

Johannes Kepler’s “Harmonices Mundi” Published

On May 15, 1618, the astronomer Johannes Kepler’s work Harmonices Mundi (“The Harmony of the World”) was published in Linz. In this dense Latin treatise, Kepler explored mathematical relationships in geometry, music, and the heavens, seeking a kind of cosmic harmony behind planetary motion. Book V contains what is now known as Kepler’s third law, linking the square of a planet’s orbital period to the cube of its average distance from the Sun. This law became a cornerstone for Isaac Newton’s theory of gravitation and marked a major step in turning the night sky into something that could be described with precise mathematical rules.

U.S. History1756

Beginning of the Seven Years’ War in North America

On May 15, 1756, Britain formally declared war on France, marking the official start of the Seven Years’ War, known in North America as the French and Indian War. Fighting had already broken out in the Ohio Valley, but the declaration turned scattered clashes into a global imperial conflict. The war redrew maps from Canada to India and left Britain with huge new territories in North America—and a staggering war debt. The Crown’s later efforts to recoup costs through colonial taxes helped ignite friction that would, within a generation, fuel the American Revolution.

World History1796

Napoleon Bonaparte Wins the Battle of Lodi

On May 15, 1796, General Napoleon Bonaparte completed his victory at the Battle of Lodi in northern Italy during his first Italian campaign. French forces forced their way across a narrow bridge over the Adda River under heavy Austrian fire, a moment that later loomed large in Napoleonic legend. The triumph allowed the French to occupy Milan days later and cemented Napoleon’s reputation as a daring and charismatic commander. He would later point to Lodi as the battle that convinced him he was destined for great things, a belief that shaped European politics for the next two decades.

Science & Industry1800

Founding of the Royal Institution in London

On May 15, 1800, the Royal Institution of Great Britain was founded in London with the support of scientists and aristocrats, including the American-born polymath Sir Benjamin Thompson (Count Rumford). Its mission was to promote the application of scientific knowledge to practical improvements in daily life, from heating and lighting to agriculture. The institution soon became famous for public lectures and demonstrations, especially those by chemist Humphry Davy and later Michael Faraday, whose Christmas Lectures brought vivid laboratory science to popular audiences. The Royal Institution helped make experimental science a visible part of urban culture and gave a platform to discoveries that shaped the 19th century.

Famous Figures1856

Birth of L. Frank Baum, Creator of Oz

On May 15, 1856, Lyman Frank Baum was born in Chittenango, New York. After dabbling in theater, retail, and journalism, he achieved lasting fame with his 1900 children’s novel The Wonderful Wizard of Oz, which introduced Dorothy, the Scarecrow, the Tin Woodman, and the Emerald City. Baum went on to write a long series of Oz books, expanding the fantasy world with new characters and lands that captured young readers’ imaginations. His work helped establish American children’s literature as a distinct, homegrown tradition and laid the groundwork for the iconic 1939 film adaptation and countless reinterpretations.

U.S. History1862

U.S. Department of Agriculture Created

On May 15, 1862, President Abraham Lincoln signed legislation creating the United States Department of Agriculture (USDA). At a time when most Americans still lived on farms, Lincoln called it “the people’s department,” intended to support agricultural science, collect statistics, and spread practical knowledge to farmers. Over time, the USDA’s responsibilities grew to include food safety, conservation programs, and nutrition assistance. Its founding underscored how central farming and rural life were to the Union effort during the Civil War and to the country’s long-term economic development.

U.S. History1869

National Woman Suffrage Association Formed

On May 15, 1869, Susan B. Anthony and Elizabeth Cady Stanton led the founding of the National Woman Suffrage Association (NWSA) in New York City. Breaking with more cautious activists, the NWSA pressed for a federal constitutional amendment guaranteeing women the right to vote rather than working state by state alone. The organization also campaigned on related issues like divorce laws and equal pay, linking suffrage to a broader vision of women’s rights. In 1890 it merged with a rival group to form the National American Woman Suffrage Association, a key force behind the eventual ratification of the Nineteenth Amendment in 1920.

World History1905

Las Vegas Officially Founded as a City

On May 15, 1905, railroad officials auctioned off 110 acres of land near the Union Pacific tracks in southern Nevada, a sale widely regarded as the birth of the city of Las Vegas. Buyers snapped up lots along what would become Fremont Street, attracted by the promise of a service hub between Los Angeles and Salt Lake City. At the time, the dusty settlement was best known for its springs and as a stopover on the railroad, not neon lights. Over the 20th century, Las Vegas’s lenient gambling laws and exuberant architecture turned that modest rail town into a global symbol of spectacle and entertainment.

Famous Figures1905

Birth of Joseph Cotten, Screen Actor of the Studio Era

On May 15, 1905, actor Joseph Cotten was born in Petersburg, Virginia. After stage work and radio roles, he became closely associated with Orson Welles and the Mercury Theatre before making his film breakthrough in Citizen Kane (1941) as the conflicted friend Jedediah Leland. Cotten’s understated intensity carried into memorable performances in films such as The Magnificent Ambersons, Alfred Hitchcock’s Shadow of a Doubt, and Carol Reed’s The Third Man. His career traced the evolution of American film from the studio system to more independent productions, and his roles helped define the look and feel of mid‑century cinema.

Science & Industry1911

Standard Oil Ordered Broken Up by U.S. Supreme Court

On May 15, 1911, the U.S. Supreme Court issued its landmark decision in Standard Oil Co. of New Jersey v. United States, ruling that John D. Rockefeller’s massive oil trust violated the Sherman Antitrust Act. The Court applied a “rule of reason,” concluding that Standard Oil’s dominance and tactics unreasonably restrained trade. It ordered the company to be split into dozens of smaller entities, several of which—like Exxon, Mobil, and Chevron—later grew into giants in their own right. The breakup became a defining moment in American antitrust enforcement and influenced how governments around the world think about monopolies and market power.

Arts & Culture1940

Nylon Stockings Go on Sale Across the United States

On May 15, 1940, nylon stockings went on sale to the general public across the United States, after earlier limited releases. Developed by DuPont chemists in the 1930s, nylon offered women a sheer, durable alternative to silk, which was expensive and subject to supply disruptions. Department stores reported long lines and rapid sellouts as customers rushed to try the new hosiery. Within a year, nylon became a staple of women’s fashion, and its later wartime rationing underscored just how quickly synthetic fibers had woven themselves into everyday life and popular culture.

World History1940

Dutch Army Surrenders to Germany in World War II

On May 15, 1940, after days of intense fighting and the bombing of Rotterdam, the Dutch commander-in-chief, General Henri Winkelman, ordered the capitulation of the Netherlands to Nazi Germany. The swift campaign shocked many observers, who had recalled the Netherlands’ neutrality in World War I. Under German occupation, Dutch society faced harsh repression, especially Jewish communities that were subjected to deportation and murder. The surrender marked another step in Germany’s rapid sweep through Western Europe in the spring of 1940 and left Britain increasingly isolated on the Allied side.

U.S. History1941

First Experimental Launch of the U.S. Jet Aircraft XP-46A

On May 15, 1941, the United States Army Air Corps conducted an early test flight of the Curtiss XP-46A fighter at Wright Field in Ohio. Intended as a more advanced successor to the P‑40, the XP‑46 program helped engineers explore higher-speed aerodynamics, armament layouts, and cockpit protection. Although the design itself did not proceed to mass production, the data and experience gathered informed later American fighter development during World War II. These incremental experiments illustrated how many prototypes and test flights lay behind the few aircraft types that ultimately saw combat service.

World History1948

Transjordan’s Arab Legion Enters the Old City of Jerusalem

On May 15, 1948, the day after the State of Israel declared independence, Transjordan’s Arab Legion moved into the Old City of Jerusalem during the opening phase of the 1948 Arab–Israeli War. Fierce street fighting broke out between Legion units and Jewish defenders in the dense, walled quarters around the Temple Mount and the Western Wall. By the end of the campaign, the Old City was under Jordanian control, while West Jerusalem remained under Israeli authority, a division that persisted until 1967. The events of that May set patterns of control and contestation in Jerusalem that remain intensely sensitive today.

Inventions1951

UNIVAC I Delivered to the U.S. Census Bureau

On May 15, 1951, the first UNIVAC I (UNIVersal Automatic Computer) was formally accepted by the U.S. Census Bureau. Designed by J. Presper Eckert and John Mauchly, it was one of the earliest commercial electronic digital computers, using vacuum tubes and magnetic tape rather than punched cards alone. The machine took up a room, generated enormous heat, and required a team of specialists to operate, yet it could process data at speeds that were astonishing for the time. UNIVAC’s deployment helped demonstrate that large‑scale electronic computing had practical uses in government and business, not just in military laboratories and universities.

Science & Industry1963

Launch of Mercury-Atlas 9, Faith 7

On May 15, 1963, NASA launched Mercury‑Atlas 9, carrying astronaut Gordon Cooper in the spacecraft Faith 7. Blasting off from Cape Canaveral, Cooper spent about 34 hours in orbit, circling the Earth 22 times in what became the final crewed flight of the Mercury program. During the mission he conducted experiments, photographed cloud patterns, and manually controlled reentry after a series of technical glitches. The flight demonstrated that an astronaut could function effectively in space for more than a day, providing data and confidence that fed directly into the more ambitious Gemini and Apollo missions that followed.

Arts & Culture1971

“Bridge Over Troubled Water” Sweeps the Grammys

On May 15, 1971, at the 13th annual Grammy Awards, Simon & Garfunkel’s “Bridge Over Troubled Water” took home multiple top honors, including Record of the Year, Song of the Year, and Album of the Year. The title track, sung by Art Garfunkel and written by Paul Simon, blended gospel influences with lush production and quickly became an anthem of comfort and resilience. The duo had already begun to split apart by the time they received the awards, giving the night a bittersweet undertone. Their wins cemented the album’s place as a touchstone of early 1970s popular music and showcased how introspective songwriting could dominate mainstream charts.

Famous Figures1972

Governor George Wallace Shot in Maryland

On May 15, 1972, during a campaign stop in Laurel, Maryland, Alabama governor and presidential candidate George Wallace was shot and seriously wounded by Arthur Bremer. The attack occurred as Wallace worked the crowd at a shopping center rally, leaving him permanently paralyzed from the waist down. Wallace, long known for his pro‑segregation stance, continued his political career from a wheelchair and later publicly renounced some of his earlier positions. The shooting forced the Secret Service and campaign teams to rethink candidate security in an era when televised rallies and open‑air appearances were central to American politics.

Inventions1997

IBM’s Deep Blue Defeats Garry Kasparov in Match Play

On May 15, 1997, IBM’s chess‑playing computer Deep Blue won the deciding game of a six‑game match against reigning world champion Garry Kasparov in New York City. The upgraded machine, capable of evaluating many millions of positions per second, defeated Kasparov by a final score of 3½–2½, the first time a sitting world champion had lost a match to a computer under standard tournament conditions. The result stunned many chess fans and captured public imagination about the capabilities of specialized computing. Deep Blue’s victory became a touchstone in debates about artificial intelligence, human creativity, and what it means to “think” in a digital age.

World History2004

South Africa’s Thabo Mbeki Begins Second Term as President

On May 15, 2004, Thabo Mbeki was inaugurated for a second term as president of South Africa at a ceremony in Pretoria following the country’s third democratic elections. Succeeding Nelson Mandela in 1999, Mbeki had focused on economic growth and African continental diplomacy, including the New Partnership for Africa’s Development. His second term unfolded amid praise for macroeconomic stability but also sharp criticism of his government’s stance on HIV/AIDS and internal party tensions. The inauguration symbolized both continuity and the evolving challenges of post‑apartheid governance a decade after the country’s first universal suffrage elections.

Science & Industry2012

First Private Space Station Resupply Launch Announced Ready

On May 15, 2012, in the final days before launch, SpaceX and NASA confirmed readiness for the company’s historic Falcon 9/Dragon mission, the first attempt by a private firm to send a cargo spacecraft to the International Space Station under NASA’s Commercial Orbital Transportation Services program. Technical reviews completed that day cleared the way for liftoff on May 22 after earlier delays. The mission would go on to demonstrate that a non‑government spacecraft could rendezvous and berth with the ISS, a milestone in the commercialization of orbital flight. The preparations and launch signaled a shift from exclusively state‑run space logistics to a model where private companies play central roles in routine access to low Earth orbit.