William, Duke of Normandy, was crowned King of England at Westminster Abbey following his victory at the Battle of Hastings, beginning the Norman era in Britain.

Virginia became the final state needed to ratify the first ten amendments to the U.S. Constitution, guaranteeing fundamental rights and freedoms to American citizens.

President Abraham Lincoln declared that all enslaved people in Confederate states were to be considered free, a pivotal moment in the American Civil War and the abolition of slavery.

Ellis Island in New York Harbor opened as the United States' first federal immigration station, processing over 12 million immigrants over the next 62 years.

Ireland formally joined the European Economic Community alongside the UK and Denmark — a decision that would transform the Irish economy and later shape the Brexit debate over the Northern Ireland border.

The euro was introduced as an electronic currency in 11 European Union member states, replacing national currencies and marking the most significant step in European monetary union.

Euro banknotes and coins were introduced in 12 European Union member states, replacing national currencies including the German Mark, French Franc, and Italian Lira in the biggest currency changeover in history.