On August 18, 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 18. They documented the region’s wildlife and prepared for a council with the Sioux tribes, advancing their exploration of the Louisiana Purchase.
• 1838: During the Mormon War in Missouri, tensions escalated. On or around August 18, non-Mormon vigilantes in Daviess and Carroll Counties continued their campaign against Mormon settlers, with increased skirmishes contributing to 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 18, Union forces were regrouping after their retreat from Springfield, while Confederate forces strengthened their control in southwest Missouri, highlighting the state’s pivotal role in the conflict.
• 1870: The Kansas City Stockyards expanded operations around August 18, reinforcing Kansas City’s position as a major livestock trading hub and boosting Missouri’s agricultural economy.
• 1904: The St. Louis World’s Fair, or Louisiana Purchase Exposition, was ongoing, with August 18 featuring international cultural exhibits and early Olympic events, showcasing Missouri’s global prominence.
• 1967: The St. Louis Cardinals played a significant game against the New York Mets at Busch Stadium on August 18, with Bob Gibson pitching a complete game and Roger Maris hitting a key home run, contributing to their World Series-winning season and reinforcing Missouri’s baseball legacy.