On June 4, 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 4, finalizing preparations for their journey up the Missouri River to explore the Louisiana Purchase. They were gathering supplies and coordinating with local officials, solidifying Missouri’s role as the gateway to western exploration.
• 1820: Missouri’s constitutional convention, held in St. Louis, was actively drafting the state’s first constitution around June 4. This was a crucial 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 a focal point of conflict. On or around June 4, Union forces under General Nathaniel Lyon were reinforcing their control over St. Louis, securing key locations like the arsenal to prevent Confederate sympathizers from gaining ground.
• 1876: The St. Louis-based Missouri Botanical Garden, founded by Henry Shaw, hosted a significant public exhibition around June 4, showcasing rare plant species and advancing its reputation as a leading botanical research center.
• 1904: The St. Louis World’s Fair, or Louisiana Purchase Exposition, was underway, with June 4 featuring early international exhibits and technological displays, highlighting Missouri’s prominence as a global cultural and economic hub.
• 1942: During World War II, the Weldon Spring Ordnance Works in St. Charles County, Missouri, was in full operation around June 4, producing explosives for the war effort, underscoring Missouri’s contribution to the national defense industry.