1. In 1870, the Missouri State Board of Agriculture was established on July 15. The board was responsible for promoting and improving agriculture throughout the state.

2. On July 15, 1933, the Missouri State Penitentiary in Jefferson City experienced one of its worst riots in history. The riot was sparked by poor living conditions and mistreatment of prisoners and resulted in the deaths of two inmates.

3. In 1961, the Mark Twain Boyhood Home and Museum was opened in Hannibal, Missouri, on July 15. The museum is dedicated to the life and works of famous author Mark Twain, who grew up in Hannibal.

4. On July 15, 1981, the World Series of Rodeo held its first competition at the Missourian Hotel and Convention Center in Columbia. The event brought together the best rodeo athletes in the world to compete for cash prizes.

5. In 2000, the American Association of State Highway and Transportation Officials approved the addition of a spur to the Mark Twain Memorial Bridge in Missouri, connecting the bridge to Illinois. The spur was officially opened on July 15 of that year.