On August 20, the following notable historical events related to Missouri have been recorded:

• 1804: The Lewis and Clark Expedition was near present-day Sioux City, Iowa, across from Missouri’s Atchison County, on or around August 20. A significant event occurred when Sergeant Charles Floyd died, likely from appendicitis, near present-day Sioux City, marking the expedition’s first and only death. The expedition, advancing the exploration of the Louisiana Purchase, was in Missouri’s vicinity during this time.
• 1838: During the Mormon War in Missouri, tensions escalated. On or around August 20, non-Mormon vigilantes in Daviess and Carroll Counties continued their campaign against Mormon settlers, with skirmishes intensifying the conflict that led to the Mormon expulsion order later in 1838.
• 1861: During the Civil War, the aftermath of the Battle of Wilson’s Creek (August 10) continued in Missouri. On August 20, Union forces were regrouping after their retreat from Springfield, while Confederate forces strengthened their control in southwest Missouri, highlighting Missouri’s pivotal role in the conflict.
• 1876: The St. Louis-based Anheuser-Busch brewery expanded its refrigerated railcar system around August 20, enabling broader distribution of Budweiser and reinforcing Missouri’s leadership in the national brewing industry.
• 1904: The St. Louis World’s Fair, or Louisiana Purchase Exposition, was ongoing, with August 20 featuring international scientific exhibits and early Olympic events, showcasing Missouri’s global cultural and economic prominence.
• 1967: The St. Louis Cardinals played a notable game against the Pittsburgh Pirates at Busch Stadium on August 20, with Bob Gibson pitching a complete game and Orlando Cepeda hitting a key home run, contributing to their World Series-winning season and reinforcing Missouri’s baseball legacy.