On July 20, including events up to the present, the following notable historical events related to Missouri have been recorded:

• 1804: The Lewis and Clark Expedition, navigating the Missouri River, was near present-day Nebraska City, Nebraska, across from Missouri’s Nemaha County, on or around July 20. They documented the river’s conditions and interactions with Native American tribes, contributing to their exploration of the Louisiana Purchase.
• 1838: During the Mormon War in Missouri, tensions escalated. On or around July 20, conflicts between Mormon settlers and non-Mormon residents in Carroll County intensified, with both sides arming themselves, foreshadowing the violent clashes that led to the Mormon expulsion later that year.
• 1861: During the Civil War, Missouri saw continued military activity. On July 20, Union forces under General Nathaniel Lyon were maneuvering in southwest Missouri, engaging in skirmishes near Springfield as they prepared for the Battle of Wilson’s Creek.
• 1875: The Missouri State Fair, held in Sedalia, was in its planning stages around July 20 for its inaugural event later that year. This fair became a cornerstone of Missouri’s agricultural and cultural heritage.
• 1904: The St. Louis World’s Fair, or Louisiana Purchase Exposition, was ongoing, with July 20 featuring international scientific exhibits and athletic competitions, including early Olympic events, highlighting Missouri’s global prominence.
• 1969: On July 20, the Apollo 11 moon landing was celebrated across Missouri, with special events in St. Louis and Kansas City. The St. Louis Science Center (then in its early form) hosted public viewings, reflecting Missouri’s engagement with space exploration.