On June 23, the following notable historical events related to Missouri have been recorded:

• 1836: The Platte Purchase was formalized, adding six counties in northwest Missouri to the state. On or around June 23, negotiations with Native American tribes, including the Iowa and Sac and Fox, were finalized, transferring land to Missouri and opening it for settlement, significantly shaping the state's borders.
• 1861: During the Civil War, Missouri remained a hotspot of divided loyalties. While no specific battle is recorded for June 23, this date falls within the period of intense militia activity and skirmishes, particularly in central and western Missouri, as Union and Confederate sympathizers clashed.
• 1904: The St. Louis World’s Fair, or Louisiana Purchase Exposition, was ongoing, with June 23 being a notable day for agricultural exhibits and international displays. The fair continued to draw global attention to St. Louis, showcasing Missouri’s economic and cultural significance.