1. The Yankees' first game at Yankee Stadium: On April 21, 1923, the New York Yankees played their first game at the brand new Yankee Stadium in the Bronx. The team defeated the Boston Red Sox 4-1 and went on to win their first World Series in the stadium's inaugural year.

2. Robert Fulton's steamboat journey: On April 21, 1807, inventor Robert Fulton made history with his steamboat voyage up the Hudson River from New York City to Albany. The trip took 32 hours and laid the foundation for steam-powered transportation across the world.

3. The Met opens its doors: On April 21, 1870, the Metropolitan Museum of Art opened its doors for the first time to the public. The museum has since become one of the most renowned art institutions in the world, with collections spanning over 5,000 years of human history.

4. JFK's first visit to New York after presidency: On April 21, 1965, former President John F. Kennedy made his first visit to New York City after leaving office. He visited the Lincoln Square Neighborhood Center in Manhattan, which was devoted to social programs for disadvantaged families.

5. First Earth Day celebration: On April 21, 1970, New York City held its first ever Earth Day celebration. The event was part of a nationwide movement to raise awareness about environmental issues and promote conservation efforts. The celebration included a rally in Union Square and a march down Fifth Avenue.