1. 1936: The first National Football League (NFL) draft took place in Philadelphia, Pennsylvania. Jay Berwanger was the first overall pick by the Philadelphia Eagles.

2. 1967: The 25th Amendment to the United States Constitution was ratified, establishing procedures for presidential succession in the event of a vacancy.

3. 1996: IBM’s Deep Blue, a chess-playing computer, defeated world champion Garry Kasparov for the first time in a match under standard chess tournament time controls.

4. 2005: North Korea publicly declared that it had nuclear weapons.

5. 2009: The communication satellite Iridium 33 and the defunct Russian satellite Cosmos 2251 collided in orbit, creating thousands of pieces of space debris.

6. 2016: Scientists at the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced the first direct detection of gravitational waves, confirming a major prediction of Albert Einstein’s general theory of relativity.