- The brightest supernova in recorded history appeared. (1006) Astronomers across several continents noted its appearance, and it is thought to be the brightest stellar event in history.
- Saigon was occupied by Communist forces. (1975) After more than 20 years of fighting, South Vietnam surrendered on this day when North Vietnamese forces overran Saigon, ending the Vietnam War.
- Adolf Hitler committed suicide. (1945) Recognizing that the war was ending, Hitler had retreated to his Fuhrerbunker several months previously. He and his new wife, Eva Braun, whom he had married the day before, committed suicide on this day.
- The first federal prison for women opened. (1927) The Federal Industrial Institution for Women opened in West Virginia as the first federal prison for women. Described as a "fashionable boarding school," the prison focused on reforming the inmates by teaching them farming and secretarial skills.
- The first presidential inauguration in the US took place. (1789) George Washington officially became the first US president on this day in an inauguration ceremony in New York, which was the first capitol of the US.
- Hail the size of oranges fell in India. (1888) The storm came up without warning, killing thousands of livestock and several hundred farmers. According to eyewitness reports, the hail was stacked 2 feet (over 60 cm) high in some places.
- The Louisiana Purchase was finalized. (1803) The agreement almost doubled the size of the US, and was an extremely favorable bargain too — America got over 820,000 square miles (over 2 million square km) of land for less than $0.03 US Dollars (USD) an acre.
- Douglas Fairbanks and Mary Pickford made their mark on the cement of Grauman's Chinese Theater. (1927) Fairbanks and Pickford were the first celebs to intentionally put their footprints in the cement outside of the theater, though the tradition is said to have been inspired by Norma Talmadge, a silent film mega-star, accidentally stepping in wet concrete the day the theater opened.
- The Boulder Dam was renamed the Hoover Dam for the second time. (1947) The order to construct the dam actually never provided a name for it, so the dam went through several naming controversies. It was originally called the Boulder Dam because of its location in Boulder Canyon, but was renamed after President Herbert Hoover. When Hoover fell out of popularity, it was renamed the Boulder Dam until it was finally officially renamed the Hoover Dam in 1947.
- Hawaii became a territory of the US. (1900) A group of American businessmen had overthrown the traditional monarchy of Hawaii several months earlier and operated the island themselves, occasionally clashing diplomatically with the US. The provisional government finally allowed Hawaii to become a US territory after receiving a guarantee that they would not be punished for the coup.