1. On September 20, 1881, the famous gunfighter and outlaw Jesse James was reportedly killed in Saint Joseph, Missouri. There is speculation that he may have actually lived out the rest of his life in hiding in New Mexico under the alias "J. Frank Dalton."

2. The New Mexico State Fair typically begins around September 20 each year. The fair features livestock shows, carnival rides, live music, and more, making it a popular destination for locals and visitors alike.

3. In 1850, the United States government signed the Treaty of Guadalupe Hidalgo with Mexico, officially ending the Mexican-American War and ceding a vast amount of land to the United States, including what is now New Mexico.

4. On September 20, 1996, the VLA (Very Large Array) radio telescope in New Mexico detected the first-ever fast radio burst, a powerful radio signal believed to be emitted from deep space.

5. September 20, 1943, marked the groundbreaking for the birthplace of the atomic bomb, the Los Alamos National Laboratory in northern New Mexico. The facility was established as part of the Manhattan Project, a top-secret government program aimed at building the world's first nuclear weapon.