1. Missouri became a state on September 24, 1821.
This day marked the admission of the Missouri Territory as the 24th state of the United States. The decision was a controversial one, as it led to the Missouri Compromise, which aimed to maintain a balance of power between free and slave states.

2. The Battle of Pilot Knob took place on September 24, 1864.
This Civil War battle was fought in Iron County, Missouri, and is notable for being the opening engagement of Confederate General Sterling Price's 1864 Missouri Expedition. Union forces successfully defended their position at Pilot Knob, slowing Price's advance and earning a strategic victory.

3. The Gateway Arch was completed on September 24, 1965.
Construction of the iconic Gateway Arch in St. Louis began in 1963 and was completed two years later. The arch is both a symbol of St. Louis and a monument to the westward expansion of the United States.

4. Missouri's first public university opened on September 24, 1839.
The University of Missouri was founded in Columbia, Missouri, and became the first public university west of the Mississippi River. Today, the university is part of the University of Missouri System and is known for its strong research programs.

5. The Missouri state flag was first flown on September 24, 1913.
The flag, which features a red, white, and blue tricolor with the Missouri state seal in the center, was designed by Marie Elizabeth Watkins Oliver and officially adopted by the state in 1913. Today, the flag is a familiar symbol of Missouri and is flown throughout the state.