1. Missouri became a state on June 12, 1821.
On June 12, 1821, Missouri officially became the 24th state in the United States. This followed the Missouri Compromise of 1820, which allowed Missouri to enter the Union as a slave state while Maine entered as a free state, ultimately keeping the balance between slave and free states equal.

2. The state flag of Missouri was adopted on June 12, 1913.
On June 12, 1913, Missouri officially adopted its current state flag. The flag features the state seal, surrounded by blue and red stripes representing Missouri's rivers and land, along with the state motto, "Salus Populi Suprema Lex Esto," which means "Let the welfare of the people be the supreme law."

3. The Route 66 Association of Missouri was founded on June 12, 1987.
On June 12, 1987, the Route 66 Association of Missouri was founded in Springfield, Missouri. The association is dedicated to preserving the history and culture of the iconic Route 66 highway, which runs through Missouri and several other states.

4. The Great Flood of 1844 peaked on June 12.
The Great Flood of 1844 was one of the worst floods in Missouri history, affecting the entire Missouri River basin. The flood peaked on June 12, with the river reaching 38.9 feet in St. Louis, causing widespread damage and loss of life.

5. The Battle of Boonville took place on June 12, 1861.
The Battle of Boonville was one of the first significant battles of the American Civil War in Missouri. On June 12, 1861, Union forces under the command of Nathaniel Lyon defeated a Confederate force led by Governor Claiborne F. Jackson, securing the Missouri River for Union use and helping to prevent Missouri from seceding from the Union.