Today:
1122 – The Concordat of Worms was signed, ending the Investiture Controversy between the Papacy and the Holy Roman Empire.
1459 – The Battle of Blore Heath took place during the Wars of the Roses in England.
1642 – Harvard College held its first commencement ceremony in Cambridge, Massachusetts.
1806 – Lewis and Clark returned to St. Louis after their expedition to the Pacific Northwest.
1846 – German astronomer Johann Galle discovered the planet Neptune at the Berlin Observatory.
1862 – U.S. President Abraham Lincoln issued the preliminary Emancipation Proclamation.
1889 – Nintendo was founded as a playing card company in Kyoto, Japan.
1932 – The Kingdom of Saudi Arabia was unified under King Abdulaziz Ibn Saud.
1962 – The Lincoln Center for the Performing Arts opened in New York City.
2002 – The first public version of the web browser Mozilla Firefox (as Phoenix 0.1) was released.