Browse Historical Events by Day: What Happened on May 15th?

German astronomer Johannes Kepler discovers the third of his three laws of planetary motion, often referred to as the "harmonic law". This law establishes a relationship between a planet's orbital period and its average distance from the Sun, specifically that the square of the orbital period is proportional to the cube of the average distance. Kepler's Third Law implies that the period for a planet to orbit the Sun increases rapidly with the radius of its orbit. More

The first emigrant wagon train, the Bidwell-Bartleson party, departs Independence, Missouri, on a 1,730-mile journey to California, traveling over the Sierra Nevada mountains. This group, consisting of 70 individuals in 15 wagons, faced starvation and exhaustion along the long trip. They way, ultimately arrived in California almost six months later on November 4, 1841. More

The National Woman Suffrage Association (NWSA) was founded in New York City by Susan B. Anthony and Elizabeth Cady Stanton. The NWSA was formed after the women's rights movement split over the proposed Fifteenth Amendment, which would grant voting rights to African American men but not to women. The NWSA opposed the amendment as written, advocating for women's suffrage along with the rights of Black men. More

The U.S. Postal Service opens its first regularly scheduled airmail route between New York City and Washington, D.C. via Philadelphia. This historic event marked the beginning of a new era in both mail transportation and aviation. More

Walt Disney's Mickey Mouse made its debut with the test screen premiere of the cartoon Plane Crazy to a theater audience and potential distributors as a silent film and it failed to pick up a distributor. Later that year, Disney released Mickey's first sound cartoon, Steamboat Willie, which was an enormous success; Plane Crazy was officially released as a sound cartoon on March 17, 1929. It ended up being the fourth Mickey film to be given a wide release after Steamboat Willie, The Gallopin' Gaucho and The Barn Dance (1929).

Brothers Richard and Maurice McDonald opened a drive-in restaurant, in San Bernardino, California. Initially called "McDonald's Bar-B-Q. In 1948 they took a risk by streamlining their operations and introducing their "Speedee" Service System featuring 15 cent hamburgers. This drive-in restaurant is considered the origin of the McDonald's fast-food chain. In 1955, Ray Kroc, a milkshake mixer salesman, saw the potential of the McDonald's concept and began franchising the business, eventually buying out the McDonald brothers in 1961. More

The first test of an Allied aircraft using jet propulsion takes place as the Gloster-Whittle E 28/39 aircraft flies successfully over Cranwell, England, The jet engine was the brain child of Frank Whittle, an English pilot and aviation engineer, . A young German physicist, Hans von Ohain, working for Ernst Heinkel, developed the world's first jet plane, the experimental Heinkel He 178. It first flew on August 27, 1939. just before WW II started on September 1, 1939. More