September 16

Owain Glyndwr is proclaimed Prince of Wales by his supporters, beginning a Welsh revolt against English rule.

Welsh nobleman Owain Glyndwr was proclaimed Prince of Wales by his supporters, launching a major and prolonged rebellion against English rule that, though ultimately unsuccessful, remains celebrated in Welsh national memory as a significant assertion of Welsh identity and self-determination.

American forces achieve a morale-boosting victory at the Battle of Harlem Heights during the Revolutionary War.

American troops under George Washington repelled a British advance on Manhattan at Harlem Heights, a modest but psychologically important victory following the demoralizing loss of New York City days earlier. The engagement, though militarily minor compared to later battles, helped restore some confidence and discipline within the struggling Continental Army during a particularly difficult stretch of the war's early campaigns.

Father Miguel Hidalgo delivers the Grito de Dolores, launching Mexico's war of independence from Spain.

In the small town of Dolores, Catholic priest Miguel Hidalgo y Costilla delivered an impassioned call to arms against Spanish colonial rule, an event known as the Grito de Dolores that ignited Mexico's eleven-year war of independence, now commemorated annually as Mexico's independence day.

Robert College is founded in Istanbul, the first American educational institution established outside the United States.

American missionaries and educators established Robert College overlooking the Bosphorus in Istanbul, creating what became the first American educational institution founded outside the United States. The college was named for its principal benefactor, New York merchant Christopher Rhinelander Robert, and it continues operating today, having educated generations of prominent regional leaders across the Balkans, Turkey, and the wider Middle East.

General Motors Corporation is founded, becoming one of the world's largest automotive manufacturers.

William Durant founded General Motors as a holding company for the Buick Motor Company and subsequently acquired numerous other automobile manufacturers, building it into one of the largest and most influential industrial corporations in American history over the following decades.

A bomb hidden in a horse-drawn wagon explodes on Wall Street outside the J.P. Morgan building, killing dozens.

A powerful bomb concealed in a horse-drawn wagon detonated on Wall Street outside the headquarters of J.P. Morgan and Company, killing dozens of people in an attack widely attributed to anarchist or radical political extremists, though the case was never definitively solved.

Malaysia is formed through the merger of the Federation of Malaya, Singapore, Sabah, and Sarawak.

Following negotiations among British colonial territories in Southeast Asia, the Federation of Malaya merged with Singapore, Sabah, and Sarawak to form the new nation of Malaysia, though Singapore would separate to become independent just two years later amid political tensions.

Nations sign the Montreal Protocol, a landmark international treaty to phase out substances that deplete the ozone layer.

Responding to mounting scientific evidence of ozone layer depletion caused by certain industrial chemicals, nations worldwide signed the Montreal Protocol committing to phase out ozone-depleting substances, an agreement widely considered one of the most successful international environmental treaties in history.

Inspiration4 launches as the first orbital spaceflight crewed entirely by private citizens.

A crew of four private citizens, with no professional astronauts aboard, launched into orbit on a SpaceX Crew Dragon capsule, spending three days circling Earth in a landmark mission demonstrating the growing feasibility of commercial human spaceflight beyond government space agencies.

The death of Mahsa Amini in Tehran sparks widespread protests across Iran demanding human rights and greater freedoms.

The death in police custody of Mahsa Amini, a young Kurdish-Iranian woman detained for allegedly violating Iran's mandatory hijab laws, ignited months of widespread protests across Iran under the slogan "Woman, Life, Freedom," representing one of the most significant challenges to the Iranian government in years.