1. The sinking of the Titanic: On April 15, 1912, the RMS Titanic sank in the North Atlantic, killing over 1,500 passengers and crew members. Many of the victims were from New York City, including millionaires and prominent figures such as John Jacob Astor IV and Isidor Straus.

2. Jackie Robinson's Major League debut: On April 15, 1947, Jackie Robinson made history as the first African American player to play in Major League Baseball, debuting for the Brooklyn Dodgers at Ebbets Field in Brooklyn, New York.

3. The Boston Marathon bombing: On April 15, 2013, two bombs went off near the finish line of the Boston Marathon, killing three people and injuring over 260 others. The attack sent shockwaves throughout the country, including New York, where security was increased at major events and landmarks.

4. The Lincoln Assassination: On April 15, 1865, President Abraham Lincoln died from a gunshot wound inflicted by John Wilkes Booth while watching a play at Ford's Theatre in Washington, D.C. However, the aftermath of the assassination had profound implications for New York City, where Booth had planned to also assassinate Vice President Andrew Johnson and Secretary of State William Seward. His co-conspirators, some of whom had fled to New York, were tracked down and arrested by government officials.

5. The birth of Leonardo da Vinci: While not directly related to New York history, April 15 also marks the birthday of one of the most famous artists in history, Leonardo da Vinci. Born in 1452 in a small town in Tuscany, Italy, Leonardo is known for his iconic works such as the Mona Lisa and The Last Supper, which many New Yorkers have been fortunate enough to see at museums like the Metropolitan Museum of Art.