1. In 1909, famous explorer Robert E. Peary reached the North Pole with his team of fellow explorers. Peary was a New Yorker who had previously attempted to reach the pole several times before finally succeeding on April 6th of 1909.

2. On April 6th, 1917, America entered World War I. President Woodrow Wilson delivered his famous war message to Congress on this day, declaring that the country must join the conflict "to make the world safe for democracy."

3. In 1938, the first Major League Baseball game was played at Yankee Stadium. The Yankees hosted the Boston Red Sox, and Babe Ruth hit the first home run in the stadium's history.

4. On April 6th, 1960, New York City's first major transit strike took place. Transit workers went on strike for 12 days, causing major disruptions to the city's transportation systems and leading to widespread chaos and frustration.

5. In 1970, New York City held its first official Earth Day celebration. The event, which had begun as a grassroots movement, was held in various locations throughout the city and attracted hundreds of thousands of participants. Earth Day has since become an annual event around the world, celebrated on April 22nd.