- April 1, 1789 – The United States House of Representatives holds its first full meeting in Federal Hall, achieving a quorum for the first time.
- April 2, 1921 – Albert Einstein arrives in New York on his first United States visit, and lectures on the Theory of Relativity.
- April 18, 1923 – In the first ever game at Yankee Stadium, the New York Yankees defeat the Boston Red Sox 4–1 on a three-run home run by Babe Ruth.
- April 24, 1913 – The Woolworth Building (pictured) opens, becoming the tallest building in the world until 1930.
- April 27, 2006 – Construction begins on the Freedom Tower.