1. 1786 – Wolfgang Amadeus Mozart’s opera *The Marriage of Figaro* premiered in Vienna, Austria. This opera is considered one of Mozart’s greatest achievements.

2. 1851 – The Great Exhibition, the first world’s fair, opened at the Crystal Palace in Hyde Park, London. It was an exhibition of culture and industry that became a symbol of the Victorian age.

3. 1884 – The Federation of Organized Trades and Labor Unions in the United States and Canada, which later became the American Federation of Labor, proclaimed that an eight-hour workday would be the full and legal day’s work from May 1st, 1886. This proclamation led to widespread strikes and, eventually, the establishment of Labor Day.

4. 1893 – The World’s Columbian Exposition, also known as the Chicago World’s Fair, opened to the public. It celebrated the 400th anniversary of Christopher Columbus’s arrival in the New World and showcased the technological achievements of the era.

5. 1931 – The Empire State Building was dedicated in New York City. At the time, it was the tallest building in the world, a title it held for nearly 40 years.

6. 1941 – The Orson Welles film *Citizen Kane*, widely regarded as one of the greatest films ever made, premiered at the Palace Theater in New York City.

7. 1950 – Guam was organized as a United States commonwealth.

8. 1960 – The Soviet Union shot down an American U-2 spy plane during a reconnaissance mission. The incident heightened tensions during the Cold War.

9. 1961 – The Prime Minister of Cuba, Fidel Castro, proclaimed Cuba a socialist nation and formally abolished multiparty elections.

10. 1971 – Amtrak (the National Railroad Passenger Corporation) began operation. It took over the passenger rail service for the majority of the United States, marking a new era for train travel in the country.