September 28th has seen numerous significant events throughout history, each leaving a lasting impact.
This article explores 20 notable occurrences on this date, from ancient assassinations and medieval battles to modern scientific discoveries and technological advancements.
Join us as we chronologically journey through these historical milestones, highlighting the events that have shaped our world.
September 28th – On this Day in History
48 BC – Assassination of Pompey the Great

Pompey the Great, a prominent Roman military and political leader, was assassinated on September 28, 48 BC. After a decisive defeat by Julius Caesar at the Battle of Pharsalus, Pompey fled to Egypt seeking refuge.
However, upon his arrival, he was betrayed by orders of the young King Ptolemy XIII, who saw an opportunity to ingratiate himself with Caesar.
Pompey was lured into a small boat under the pretense of a formal welcome but was stabbed to death before he could set foot on Egyptian soil. His assassination marked the end of his illustrious career and underscored the ruthless political maneuvers of the period.
235 – Resignation of Pope Pontian
Pope Pontian, who served as the Bishop of Rome from 230 to 235, was forced to resign on September 28, 235. During his papacy, Pontian faced the harsh persecution of Christians under Emperor Maximinus Thrax.
Also Read: September 27 Events in History
Eventually, Pontian was arrested and deported to the infamous mines of Sardinia, a punishment designed to be both torturous and lethal. Aware that his prolonged absence would harm the Church, Pontian resigned to ensure the continuity of leadership.
His act of self-sacrifice is remembered as a testament to his commitment to the faith, and he was later venerated as a martyr.
351 – Defeat of Magnentius by Constantius II
On September 28, 351, Roman Emperor Constantius II triumphed over the usurper Magnentius at the Battle of Mursa Major. This conflict was part of a larger struggle for control of the Roman Empire following the death of Constantius’ father, Constantine the Great.
Also Read: September 29th – On this Day in History
Magnentius had declared himself emperor in the West, leading to a civil war. The battle was one of the bloodiest in Roman history, with heavy casualties on both sides. Constantius’ victory solidified his rule over the empire but at great human cost. The defeat of Magnentius marked a crucial turning point in the consolidation of Constantius’ power.
935 – Murder of Saint Wenceslas

Saint Wenceslas, the Duke of Bohemia, was murdered on September 28, 935, by his brother Boleslaus I. Wenceslas was known for his piety and efforts to spread Christianity throughout his duchy.
His reign was marked by a commitment to Christian principles and the protection of his people. However, his policies and alignment with Christian practices created enemies among the traditionalist pagan nobility.
His brother, Boleslaus, seeking power and influenced by these factions, orchestrated Wenceslas’ assassination. Wenceslas’ death at the hands of his brother shocked the Christian world, and he was soon venerated as a martyr and a saint, symbolizing the struggle between Christianity and paganism in early medieval Europe.
1066 – William the Conqueror Invades England
On September 28, 1066, William the Conqueror, Duke of Normandy, landed on the shores of England, initiating the Norman Conquest. William’s claim to the English throne was based on promises and familial ties, which were contested by Harold Godwinson, who had been crowned king.
The invasion marked the beginning of a significant military campaign that would culminate in the Battle of Hastings on October 14, 1066.
William’s successful invasion and subsequent victory at Hastings dramatically altered the course of English history, leading to Norman rule, extensive cultural and administrative changes, and the integration of Norman customs and language into English society.
1106 – Battle of Tinchebray: Henry I of England Defeats Robert Curthose
On September 28, 1106, King Henry I of England decisively defeated his older brother, Robert Curthose, Duke of Normandy, at the Battle of Tinchebray. The battle was the culmination of a long-standing rivalry between the two brothers, both sons of William the Conqueror.
Henry’s victory at Tinchebray enabled him to reunite England and Normandy under a single rule, strengthening his position and consolidating his power. Robert was captured and imprisoned for the remainder of his life, eliminating a significant threat to Henry’s rule.
This battle is a pivotal moment in the history of the Norman kings of England, showcasing the brutal family conflicts that shaped medieval European politics.
1238 – Surrender of Muslim Valencia to King James I of Aragon
The city of Valencia, a key Muslim stronghold in Spain, surrendered to the forces of King James I of Aragon on September 28, 1238. This event was a significant milestone in the Reconquista, the centuries-long effort by Christian states to reclaim territories controlled by Muslims on the Iberian Peninsula.

James I, known as James the Conqueror, led a well-planned and executed siege that forced the city’s defenders to capitulate. The fall of Valencia not only expanded James I’s realm but also marked a crucial step in the Christian reconquest of Spain, contributing to the eventual unification of the Spanish kingdoms.
1542 – Juan Rodríguez Cabrillo Discovers California
On September 28, 1542, Portuguese explorer Juan Rodríguez Cabrillo, sailing under the flag of Spain, became the first European to discover California.
Cabrillo’s expedition reached what is now San Diego Bay, marking the beginning of European exploration and eventual colonization of the Californian coast. His journey provided valuable information about the region’s geography and its indigenous peoples.
Cabrillo’s discovery was a significant event in the Age of Exploration, opening the door to further Spanish expeditions and the eventual establishment of missions and settlements along the Californian coast, which played a crucial role in the expansion of Spanish influence in North America.
1781 – Siege of Yorktown Begins
The siege of Yorktown began on September 28, 1781, when American forces, supported by a French fleet, encircled British troops led by General Lord Cornwallis in Yorktown, Virginia. This joint Franco-American operation was a decisive moment in the American Revolutionary War.
The American troops, commanded by General George Washington, and the French forces, led by General Rochambeau, coordinated a series of maneuvers and artillery bombardments that trapped the British forces.
The siege lasted several weeks and culminated in the British surrender on October 19, 1781. This victory effectively ended major military operations in the American Revolution, leading to negotiations that eventually resulted in the Treaty of Paris and the recognition of American independence.
1787 – Congress of the Confederation Votes to Send the Constitution for Ratification
On September 28, 1787, the Congress of the Confederation took a critical step in the formation of the United States by voting to send the newly drafted Constitution to the states for ratification.
This decision followed the Constitutional Convention, where delegates had created a new framework for government to replace the Articles of Confederation, which had proven inadequate. The proposed Constitution outlined a stronger federal structure with a system of checks and balances among the executive, legislative, and judicial branches.
Sending the Constitution to the states set in motion a robust public debate and a series of state conventions that ultimately led to its ratification, laying the foundation for the current government of the United States.
1823 – Execution of Agustín de Iturbide, Emperor of Mexico

Agustín de Iturbide, who had played a crucial role in Mexico’s independence from Spain, met a tragic end on September 28, 1823. Initially a royalist officer, Iturbide switched sides and joined the independence movement, ultimately leading to the successful establishment of an independent Mexican Empire in 1821.
He was crowned Emperor Agustín I in 1822, but his rule faced significant opposition. In 1823, republican forces led by Antonio López de Santa Anna and Guadalupe Victoria forced his abdication.
After a brief exile in Europe, Iturbide returned to Mexico, believing he could help his country. However, he was arrested upon arrival and executed by firing squad, marking a dramatic end to his controversial and tumultuous career.
1867 – Toronto Becomes the Capital of Ontario
On September 28, 1867, Toronto was designated the capital of the newly formed province of Ontario. This decision came shortly after the Canadian Confederation on July 1, 1867, which unified the provinces of Canada, New Brunswick, and Nova Scotia into the Dominion of Canada.
Toronto’s selection as the capital of Ontario was influenced by its strategic location, economic importance, and growing population.
As the capital, Toronto became the political and administrative center of Ontario, spurring its development into one of Canada’s most important cities. This event marked a significant step in the city’s evolution and the broader process of nation-building in Canada.
1889 – Definition of the Length of a Meter by the General Conference on Weights and Measures (CGPM)
On September 28, 1889, the General Conference on Weights and Measures (CGPM) took a monumental step in standardizing international measurements by defining the length of a meter. This definition was based on a prototype meter bar made of an alloy of platinum and iridium, stored at the International Bureau of Weights and Measures (BIPM) in Sèvres, France.
The meter had previously been defined by the distance between two marks on a bar of platinum, and this new definition aimed to provide a more stable and precise standard. The decision by the CGPM was pivotal in ensuring consistency in scientific measurements and facilitating international trade and communication.
1924 – First Aerial Circumnavigation Completed by the US Army
On September 28, 1924, a team from the United States Army Air Service completed the first aerial circumnavigation of the globe. The journey began on April 6, 1924, with four Douglas World Cruisers and a crew of eight aviators.
The mission aimed to demonstrate the potential of air travel and the capabilities of the US military. The team faced numerous challenges, including harsh weather, mechanical failures, and logistical hurdles.
Despite these obstacles, they successfully completed the 175-day expedition, covering approximately 26,345 miles (42,398 kilometers). This historic achievement showcased the advancements in aviation technology and underscored the importance of global connectivity.
1928 – Discovery of Penicillin by Sir Alexander Fleming
On September 28, 1928, Scottish bacteriologist Sir Alexander Fleming made a groundbreaking discovery that revolutionized medicine.
Fleming noticed that a mold, later identified as Penicillium notatum, had contaminated a petri dish of Staphylococcus bacteria in his laboratory at St. Mary’s Hospital in London. He observed that the mold effectively killed the surrounding bacteria, leading him to identify the antibacterial properties of penicillin.
This discovery marked the beginning of the antibiotic era, providing a powerful tool to combat bacterial infections. Penicillin’s development and mass production during World War II saved countless lives and paved the way for the creation of other antibiotics, fundamentally changing the landscape of modern medicine.
1939 – Nazi Germany and the Soviet Union Agree on the Division of Poland
On September 28, 1939, Nazi Germany and the Soviet Union signed the German-Soviet Boundary and Friendship Treaty, effectively agreeing on the division of Poland following their joint invasion.

This pact was an extension of the Molotov-Ribbentrop Pact, signed a month earlier, which included a secret protocol dividing Eastern Europe into spheres of influence.
As a result, Poland was partitioned along the Bug River, with the western part falling under German control and the eastern part under Soviet control.
This agreement solidified the temporary alliance between the two totalitarian regimes and marked the beginning of a brutal occupation that had devastating consequences for the Polish population, including widespread atrocities and the suppression of Polish sovereignty.
1951 – CBS Makes the First Color Television Sets Available for Sale
On September 28, 1951, CBS (Columbia Broadcasting System) made the first color television sets available for sale to the general public.
These sets were based on the CBS field-sequential color system, which was the first color broadcasting standard to be approved by the Federal Communications Commission (FCC). However, the technology had significant limitations, including incompatibility with existing black-and-white television sets and a high cost of production.
Despite these challenges, CBS’s attempt marked an important milestone in the evolution of television technology. Unfortunately, the product was discontinued less than a month later due to low sales and the rapid development of more compatible and efficient color systems, but it paved the way for future advancements in color broadcasting.
1963 – First Exhibition of Roy Lichtenstein’s Whaam!
On September 28, 1963, Roy Lichtenstein’s iconic painting “Whaam!” was first exhibited at the Leo Castelli Gallery in New York City. “Whaam!” is one of Lichtenstein’s most famous works and a prime example of the pop art movement. The painting, inspired by comic book art, depicts a dramatic aerial battle with a bright, bold, and graphic style.
Lichtenstein’s use of Ben-Day dots, speech balloons, and onomatopoeia mimicked the aesthetics of mass-produced comic strips, challenging traditional notions of fine art.
The exhibition of “Whaam!” marked a significant moment in the acceptance and celebration of pop art, which sought to blur the boundaries between high art and popular culture, reflecting the changing landscape of post-war American society.
2008 – SpaceX Launches the First Private Spacecraft, the Falcon 1, into Orbit
On September 28, 2008, SpaceX achieved a historic milestone by successfully launching the Falcon 1, the first privately developed liquid-fueled rocket, into orbit. This accomplishment marked a turning point in the aerospace industry, demonstrating that private companies could effectively design, build, and launch orbital rockets.
The successful fourth flight of Falcon 1 followed three previous failures, highlighting the perseverance and innovation of the SpaceX team. The mission carried a small payload for NASA and laid the groundwork for future missions, leading to the development of more advanced rockets like the Falcon 9 and the Dragon spacecraft.
SpaceX’s success revolutionized space exploration, paving the way for increased private sector involvement and the commercialization of space travel.
2020 – Launch of the James Webb Space Telescope Delayed
The launch of the James Webb Space Telescope (JWST), originally scheduled for September 28, 2020, was delayed. The JWST is a joint project of NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA), designed to be the premier observatory of the next decade.
It aims to succeed the Hubble Space Telescope by providing unprecedented resolution and sensitivity to study the formation of stars and galaxies, exoplanets, and the origins of life.
The delay was attributed to technical challenges and the impact of the COVID-19 pandemic on the project’s timeline. The rescheduled launch aims to ensure the telescope’s systems are fully operational and capable of achieving its ambitious scientific goals.