In history:
April 21, 753 BC, is the traditional date on which Romulus founded Rome.
April 21, AD 1789, John Adams was sworn in as first Vice President of the United States nine days before George Washington was sworn in as President.
In 1962 on this date, the Seattle World’s Fair opened — the first World’s Fair in the United States since World War II. Three years later, to the day, the 1964 – 1965 New York World’s Fair opened for its second and final season.