On June 6, the following notable historical events related to Missouri have been recorded:

• 1804: The Lewis and Clark Expedition was in the St. Louis area on or around June 6, finalizing preparations for their journey up the Missouri River to explore the Louisiana Purchase. They were completing logistical arrangements, reinforcing Missouri’s role as the gateway for western exploration.
• 1820: Missouri’s constitutional convention, held in St. Louis, was actively drafting the state’s first constitution around June 6. This was a critical step toward Missouri’s admission as a state in 1821, amid national debates over slavery tied to the Missouri Compromise.
• 1861: During the Civil War, Missouri was marked by escalating tensions. On or around June 6, Union forces under General Nathaniel Lyon were securing St. Louis, conducting operations to prevent Confederate sympathizers from seizing control of key infrastructure like the St. Louis Arsenal.
• 1873: The Missouri, Kansas, and Texas Railway (Katy Railroad) began expanding its network through southwest Missouri around June 6, connecting Springfield to other regions and fostering economic growth in the state.
• 1904: The St. Louis World’s Fair, or Louisiana Purchase Exposition, was underway, with June 6 featuring early international trade exhibits and cultural performances, highlighting Missouri’s prominence as a global hub.
• 1944: On D-Day, June 6, Missouri contributed significantly to the war effort. The state’s Weldon Spring Ordnance Works was producing explosives, and Missouri soldiers, including those from the 29th Infantry Division, were involved in the Normandy invasion, underscoring Missouri’s role in World War II.