- Edward Jenner tested a smallpox vaccine. (1796) Jenner developed the vaccine after observing that milkmaids who had contracted cowpox, a similar disease, were rendered immune to smallpox. The vaccine was a success, and smallpox was completely eradicated about 200 years later.
- The first US Olympics were held. (1904) The 1904 Olympics were only the third modern Olympics, and the first held in the US. Held in St. Louis, Missouri, the event was mostly overshadowed by the World's Fair.
- Lewis and Clark departed on their expedition. (1804) Their exploratory expedition lasted over two years, during which time they became the first Europeans to see much of the American West.
- The Warsaw Pact was formed. (1955) Responding to the newly formed NATO, the USSR and many of its satellite states signed a pact that gave the USSR control of military forces in the region. The pact remained intact until 1991, when it fell with the USSR.
- Israel became a state. (1948) Though an emotional event for many Jews, the creation of the state of Israel was not very popular with surrounding Arab countries, and fighting in the region flared up immediately — the next day, a coalition of surrounding countries attacked Israel.
- Skylab was launched. (1973) Skylab was the first American space station, and hosted various missions for five years before the empty space station unexpectedly deteriorated and crashed.
- The Rockefeller Foundation began operating. (1913) Inspired by Andrew Carnegie's philanthropy, John Rockefeller started the foundation off with $100 million US Dollars (USD). It has helped establish, among other things, the first school of Public Hygiene and Health in the US, several large virus research centers, and the War and Peace Studies, which helped influence US foreign policy in World War II.
- Mrs. Dalloway was published. (1925) The novel is considered one of Virginia Woolf's best, and was revolutionary in its time for its themes of neuroses, homosexuality, and feminism.
- Frank Sinatra died. (1998) Sinatra was an iconic American performer through several decades, and was one of the famous Rat Pack group of performers. Besides his singing, he also acted in several high-profile movies, including Ocean's Eleven and The Manchurian Candidate.
- Lina Medina became the world's youngest confirmed mother. (1939) Medina was five years old when she gave birth to a son in Peru. She is thought to be a case of extreme precocious puberty, where the body goes through puberty at an very young age, since she already had prominent breasts and was menstruating by the time she was four. The father of the child was never identified.